If you're not married to building a completely man-made mine, the answer is to find a deep tunnel.

Getting down to the bottom is correct, as that is where the highest concentration of useful minerals is located, but digging a tunnel doesn't expose you to nearly the same amount of blocks as using a generated cave system.

In my primary game, I dug a mine down to the bottom, clearing out a large amount of stone, which only resulted in some coal, and very few iron, where as at the bottom I discovered a cave network (filled with lava, but some water solved that), which resulted in a large amount of coal and iron, as well as diamond and gold.

I've dug straight down to bedrock as well and at the bottom carved out a 40 long by 20 wide room 4 high. This netted me a full stack of redstone, lots of lava. 2 diamond, lots of coal, almost no iron.

The straight down to bedrock approach I find is really good for redstone but not much else. I find that in the generated caves there is a lot more ore along the walls. So you really need both I think.

I've made a waterfall going down my vertical bedrock mine shaft and shoot up to the top with a boat for fast surface access.

I find the easiest way to get to the bottom of a mineshaft is to set your ladder 2 blocks onto the wall. That way you can carefully fall almost the entire way to the bottom and simply hold the backwards key to reattatch yourself to the ladder just before you hit the ground.

There is a great wiki with some number crunching.

I use this in single player:

▒▒██▒▒__▒▒__   ██ blocks you should mine
▒▒██▒▒__▒▒__   ▒▒ blocks you can see
__▒▒__▒▒██▒▒   __ blocks you can't see if you don't mine ▒▒ blocks
__▒▒__▒▒██▒▒   Repeat this pattern as many times as needed

Normally, I have a 2x1 trunk, and branches like a standard branch mine, but instead of just going outwards from the trunk, I go up one level and out, skip two blocks, then down one level and out. I leave two blocks between branches. And I leave two blocks between floors, and line up the branches the same between floors.

There are some areas left unexplored by this pattern, but they are thin, and it is unlikely that a diamond vein with spawn entirely within that narrow region. (About 3% will). The larger number of blocks uncovered are far more likely to contain diamonds.

If your high density branch mine gets you 100% diamonds, the low density branch mine would give you 212.6% ores in the same time, minus 3% from the earlier probability worked out before.

Also, you ought to build it so that the floor of the lowest tunnel is on level 11, to avoid falling in lava. If you find that there are few cave systems near your mine, feel free to dig lower, but caves tend to cluster, and caves level 10 and below are filled with lava.

I dig my main tunnel on both sides of the area I want to cover, then dig back and forth in a zigzag patten, which means I'm always digging, never walking.

I'm not sure if this is true anymore, but it used to be that larger deposits were formed by the word generator in multiplayer, so you were less likely to miss diamond deposits when using a wider mining pattern. Thus, this pattern

▒▒██▒▒____▒▒____  ██ blocks you should mine
▒▒██▒▒____▒▒____  ▒▒ blocks you can see
__▒▒____▒▒██▒▒__  __ blocks you can't see if you don't mine ▒▒ blocks
__▒▒____▒▒██▒▒__     Repeat this pattern as many times as needed

is more efficient.

As for transit? I use a long two wide straight staircase that goes all the way to bedrock. Minecarts work well for getting me deep into the mine.

Just dig 2 high in one direction for a very long time, say around an hour... it's not like you'll run out of map.

Then move 3 or four along once you've used half of your axe/s, and go back to where you started.

This will yield more in terms of ore versus time, as you are not mucking around walking between shafts and veins, and are spending almost all the time mining. Bring with you a diamond pick axe, and a shovel, since dirt and gravel still spawn underground. Use the cobblestone you will inevitably mine for traversing lava pools, and make sure you have torches (place them every 10 or so blocks).

The easiest way to mine is to mine a 2x2 tunnel horizontally. You can cover 8 blocks that way, with the same amount of blocks mined as a branch mine, which only reveals 6 blocks. As for getting up and down, use a water fall cushion (to jump into, must be 2 deep) and a water LADDER (check the youtube videos to see what it is).

personally for getting up and down I use 2 vertical shafts, one completely filled with water, and the other with a 1 block deep layer of water at the bottom and use a boat

I've found that no matter which mining pattern I used I my diamond finds were barely enough to keep me in diamond pickaxes for mining diamonds. It was a vicious circle. I've started mining with TNT now and it's much faster. Here's how I do it:

I use the branch mining technique. For a branch off the trunk I'll use 64 TNT and 32 torches. I'll dig a 2-high tunnel off the trunk, placing a torch every 10 blocks in. When I run out of torches I know I'm 320 blocks away from the trunk.

Now I'll place a block of cobblestone on the ground at the very end with a block of TNT on top. Then I back up while placing cobblestone on the ground only, putting a block of TNT on top of every 5th cobblestone block so there are 4 empty spaces between TNT blocks.

When I get back to the trunk I set off the TNT and then run along behind the blast placing torches on the wall as I go. When I get to the end I walk back to the trunk mining whatever I see along the way and picking up anything on the ground.

Each trunk takes me about 30 minutes to dig, blast and mine. I use only a fraction of a diamond pickaxe in the process. I've been mining 12-13 levels up from the bottom and getting 15-20 diamonds per trunk. The most tedious part is collecting the sand to make the TNT. I have a mob trap that I use to collect the gunpowder at night.

Give it a shot and see what you think, it's working well for me. I have mine cart tack with periodic boosters running along my trunk line to get me back and forth to my storage area quickly.

When you find a dirt vein, pursue the dirt vein till it is exhausted (usually coming away with 5-10 coal, with the potential of getting 5-10 iron, 2-6 red, 2-6 blue, and/or 1-5 gold.) Dirt is so much easier and cheaper to mine, since you only need a shovel, and it mines twice as fast as cobblestone.

When you hit bedrock mine out all the dirt, and open a huge main mine area (roughly 75/75 blocks. You can get another 40 or so Iron, 20 or so Gold and Diamond, and atleast another 120 redstone (Well, that's what I got anyawy. I might have been really lucky).

Also, to save on resources, use stone picks and shovels instead of iron.

Dig down to bedrock with a staircase. Then make a room about 10 by 10. Finally branch out on each side of the wall. Pick one side and go with it untill it is to long. Then get another side. Once all four are branched, branch off them. I now have about 15-20 BLOCKS of diamond 20-23 BLOCKS of gold like 30-50 stacks of coal no red (I don't mine it just go around) and 40-45 BLOCKS of iron all totaling about 7 hrs of work

try to find a huge, generated cave, the deepest place of that cave sometimes has diamond. Most of the time you'll find dungeons too, if you set your difficulty on peaceful, its very easy to get it

Referring to your edited question about the distances to and from your mine:

For the way down to my mines I usually use a minecart.
For the way up, this would be a nice construction: Piston Elevator

In regards to getting to and from your mine:

My solution is to never leave the mine. Bring down some saplings, some wheat seeds, and whatever else, and build your base underground near your mine. It's a lot safer and more predictable than living on the surface, since you can completely light your cave system.

The only downside is that eventually your character turns pale and starts muttering about "My precious..."

Have you ever thought of getting the minions mod? Once you get it you have to get up to 8 levels of experiance (8 levels is recomended) then you press the "m" key then commit to evil in which you then pick one of three things, repeat untill you get the master staff, with it you right click the ground four times, one minion will appear wherever you right click in those four times. Once you have your four minions, you press the "m" key again and select the "dig mineshaft", once you have selected(right clicked) where the mineshaft is going to be, your minions will automaticly dig the mineshaft down into bedrock and place a cobblestone staircase. Once they finish that then you can press the "m" botton (once again!) and select "strip mine", once you have selected an area then one minion will work on it, going a certain number of blocks forward.

A nice method if you don't like staircasing down is to mine a 1x2 tunnel down to bedrock and then using water to get up and down. To get down, drop a water bucket in and then remove it to float down with the water. To get up, simply place blocks of water above you and then remove and replace them to work your way up. Also, mining around y 3-6 is a good strategy.

Addressing your travel concerns:

Dig a shaft straight down, with water a block or two deep on the bottom, for fast downwards travel.

Build a Nether portal on the surface, transfer to Nether to spawn a matching portal there. Jump down your drop shaft, then build another portal on the bottom - it will be close enough that it should link to the same Nether portal as the surface one (but the spawning algorithm should have placed the Nether portal closer to optimal coordinates for the surface one so it will be still preferred when traveling from Nether), so you will only need to exit and reenter the same portal in Nether and you'll be transported from the bottom to the surface portal.

For horizontal travel underground still nothing beats railway - if you plan to use horses, you will have to make rather big corridors.

The advantages are definitely cost and simplicity of both solutions (note: you can cast the portals with lava buckets instead of digging obsidian, if you don't want to make a diamond rock pick) and speed - both solutions are faster than most of alternatives offered by others.

The disadvantage is Nether portals are somewhat fickle. Your portal might link to the bottom portal instead of the top one, if the corresponding Nether space happens to be an extremely tall chamber. If you have any other Nether portals within several chunks, chances are you'll get linked to their corresponding Nether exits instead. It's nothing you can't overcome with a calculator, a stack of Netherrack and 10 blocks of obsidian (sorry, can't cast lava into Obsidian in Nether) to place a portal at the correct point in Nether manually, but with a little bad luck the trivial task becomes a rather daunting one, if the "correct point" happens to be an air block far above an enormous lake of lava. Nevertheless, always build a housing around the Nether portal so that a stray Ghast fireball doesn't extinguish it.

All of the previous answers focus on minimizing blocks mined. However, if you're interested in minimizing time, there is a vastly faster late game strategy than anything discussed above.

The approach, is to use a Diamond pickax, enchanted with Level 5 efficiency, and a Haste level II Beacon. With this setup, you mine stone instantaneously and can clear cut vast swaths of stone in very little time, exposing significantly more blocks / minute than with branch mining.

Ethos discusses this in one of his videos.

Here's a good method for getting up and down from your mine quickly without needing elaborate water elevators or expensive minecart tracks.

First, get some sticks and build at least one full stack of ladders.

Then, dig a single-block column into a mountain two-high and three long. Place a torch at the far end on top for lighting. Then dig three down into your column, and place your ladders heading up to the face of the mountain where your column starts.

Dig away from the ladder into the column, two blocks high and three blocks out, and then down as you did with your initial colum, placing torches and ladders in likewise positions. Continue to mine downward in this manner, and you should have a 'staircase' that looks like this: (X = Walls, O = Open Space)

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
OOOOXXXXXXXXXXXXXXXXXXXXXXXXXXX
XOOOXXXXXXXXXXXXXXXXXXXXXXXXXXX
XOOOOOOXXXXXXXXXXXXXXXXXXXXXXXX
XOOOOOOXXXXXXXXXXXXXXXXXXXXXXXX
XXXXOOOXXXXXXXXXXXXXXXXXXXXXXXX
XXXXOOOOOOXXXXXXXXXXXXXXXXXXXXX
XXXXOOOOOOXXXXXXXXXXXXXXXXXXXXX
XXXXXXXOOOXXXXXXXXXXXXXXXXXXXXX
XXXXXXXOOOOOOXXXXXXXXXXXXXXXXXX
XXXXXXXOOOOOOXXXXXXXXXXXXXXXXXX
XXXXXXXXXXOOOXXXXXXXXXXXXXXXXXX

What this creates is a three-deep 'step' that you can walk down without having to worry about fall damage, and a ladder back to the surface going the opposite direction.

It may take a bit of experimenting to get it just right, and you can't hesitate when walking into it or you'll accidentally climb the ladder a little and take some fall damage (very minor). To reduce the chance of this, you can use a two-deep step instead, though it won't be as fast going down.

The additional benefit of the three-long column is that the middle of each 'step' makes a perfect starting place for branch mining once you reach your desired depth.

This a well covered question already but the technique I personally use isn't listed so I figure I'll add it to the mix. It isn't the technique for strip mining a chunk and extracting absolutely everything but it does expose lots of extra unseen blocks.

It is much faster for quickly gaining things you want, it's incredibly easy to do, and is also less wearing on your pickaxes.

Getting down to and up from the mine:

Use water held up by a sign at the bottom of a 1x1 shaft that is straight down starting up at the surface for dropping to diamond ore levels.
To make it, dig a 1x3 section (so you don't mine beneath your feet) leave one side open for the drop shaft, fill the middle with cobble, and place ladders in the other shaft.

The drop can be as great a distance as you want as long as the bottom of it looks like this:

o = Stone
X = Dug out
W = Water
S = A Wood Sign
L = Ladder

o X o L o
o X o L o
o X o L o
o W o L o
o S o L o
X X X L X ( This is the mine )
X X X L X

The drop is quick and completely safe. I use ladders for the return trip up but, if you prefer, (I think they take too long to make and are unreliable) you can make boat-waterfall ladder for coming back up.

Mining:

1: Dig the standard 2x1 tunnels away from your entry point. I personally do this standing at Y: 9 so I occasionally run into unexplored caves but, if you are scared of cave mining, do it at Y:8 or Y:7. I don't suggest going to a lower depth than this because bedrock can get in the way, and ore veins that are beneath your feet will be smaller.

2: Every 4th block into your tunnel dig the upper blocks in a 1x1 shaft as far as you can reach on both sides of your tunnel. If you see an ore you like, dig the bottom out and go get it!

The view of walls of your 2x1 tunnel would look like this

x = dug out
o = stone
o o o x o o o x o o o x o o o x o o o x o o o x o o
o o o o o o o o o o o o o o o o o o o o o o o o o o

Extra optional step:

3: If you want to squeeze more out of this type of mine, return once you have finished a good section and bring pieces of TnT. Place them in the back of the 1x1 shafts in the sides of your mine and set them off with Flint n Steel. I don't always do this because making TnT is a pain... but it does work.

General Mining Tips:

1: When mining always place torches on the right wall. When you want to come back just turn around and follow the torches that are now on your left. This is a very helpful technique for not getting lost in any mine exploring or digging.

2: If you have a well enchanted diamond shovel, dig out the sections of dirt you come across. High level shovels obliterate dirt at an insane speed and this typically reveals interesting stuff.

Hope this helps!

i would like to add some (CREATIVITY) to the branch mining.

conventional branch mining is explained above. also in seven sided die's answer there is mention that veins occur in 2x2 blocks.

we generally think mining in term of 2d lets consider the third dimension.

(this is just an illustration) so the wool is to show that 4 spaces are left between corridors.

reason for leaving 4 spaces :-

• (Assuming that veins occur in 2x2 blocks) the vein has possibility of appearing in center 2 block (out of 4 wool block i.e pink and blue wool in this figure) so it can be spotted while mining corridors on alternate floor (1st , 3rd , 5th, .....)

• same rule of possibility of spotting veins apply to corridor on (2nd , 4th , 6th, .....)

• the above shows the possible center block vein. block adjacent to cyan and maroon (in shown figure) can be easily seen so no doubt about that.

so this method reduces number of blocks mined and increases efficiency with respect to time.

Key assumptions : veins appear in 2x2xX(there is very very less probability of generating 1x1x1 vein ).

This is an update regarding all the new version released since this question as been asked as to date it is the 1.8.X).

Mojang made some change in the generation of resources and cave. As the branch mining was used by almost all player, Mojang decide that this was not supposed to be the best case to Find resources, as the cave where supposed to be what they wanted be the ground generation was bad at that time.

So to counter optimised mining (using tech as describe above on the layer 11 so you don't have lava lake).

So they change to generation code to make more resources spawn inside cave, and create better cave around the Map.

Exploring is now almost always more efficient then optimise mining. You can still use optimise mining so you can find part of the cave at the good range of level for diamonds for example (like this you can have diamonds, redstone, lapis, iron and gold).

I took this to the extreme and after of ~30 hours of minecraft with maxed out equipment I got this results:

Cave mining: ~80 diamonds, ~350 iron ore, ~90 gold, ~250 redsone blocks

Branch mining: ~140 dia, ~200 iron, ~60 gold, dunno how much RS

Mining out a space 100x100x10 blocks (exactly): ~15 dia, ~100 iron, ? gold, ~150 RS blocks.

X-Ray, 2 hours: ~280 dia ore, ~150 iron, ~110 gold, ~20 RS blocks, 25 emeralds.

Each method was good for somthing: The cave method for Iron & RS, the Branch mine for diamonds and the last method for losing time, getting tons of stone and breaking all your pickaxes. Then the x-ray method was super, max diamonds, no coal, no Redstone. That's it.
Note that the branch mine has each branch, even the main ones 350 blocks long

There have been quite a few possible improvements to mining since most of the other answers were posted.

First of all, transportation from the top to the bottom: water elevators. With update 1.13, water mechanics were improved, including a easy way of setting up super fast water elevators.

All you need on the way down is the old school method: water at the very bottom prevents any damage from a long fall.

On the way up, however, you can put Soul sand under a water elevator, which gets you to the top in a matter of seconds, and as a bonus prevents any drowning because Soul sand produces bubbles, as shown on the image:

Next, you can fit into a space that is one block high! There's two methods of getting this working.

1. Using an Elytra to fly into the small space by flying into the one block. Here's the setup:

It may seem like you will have a hard time mining with your head in stone, but you do not take any suffocation damage and the point of view looks like this:

2. Swimming into the hole. This method is very similar to the Elytra method. You place some water, start swimming in it and swim into the 1x1x1 gap. It is easier to set up than getting an Elytra, but it requires having to carry a bucket of water at all times.

Unfortunately, as of version 1.14, both these methods were massively downgraded, as there is a huge movement speed penalty (maximum speed is about the same as when sneaking), because the player remains in the flying/swimming position:

Even after the downgrade, the blocks revealed over time ratio is still slightly higher than digging a 2x1 corridor, and you don't have your head stuck in the block above anymore.

The final tip I have is using subtitles. This may seem like a dumb or useless feature to use while mining, but for me it works like a cave finder. If you are mining around Y coordinate 10, which most players do, you will be able to track nearby caves very easily. Whenever you see the subtitle "lava pops", you know you are near a cave. Look in the direction the subtitles tell the sound comes from, and start digging. The sounds that are coming from a distance and are detected by the subtitles are nearly undetectable by plain listening (at least for me).

So, if you like exploring caves, this is the way to massively boost your chances of finding one.

There are different strategies for different ores. Gold is most common in mesa biomes. If you can find a mesa biome, try to go mining around in it, you will soon find gold.

Diamonds are most common between height 5 and 12. If you try strip-mining, I recommend mining forward for how long you want, then turn and mine a few blocks in another direction, and then start mining the opposite direction that you started mining at. This way, you will not miss any diamonds. If you are in a cave, try mining around lava, or look for diamonds near lava. If you are near height 5-12, there are very likely diamonds near lava, and you can find diamonds buried in some stone nearby, where people could miss. I have found diamonds buried in stone near lava lots of times.

I don't have many tips for emeralds, but if you don't know, emeralds can only be found in extreme hills biomes, and found between levels 4-32, but height level 11 is your best option. Emeralds can also be found in village chests, villager trades, and drops by illagers during a raid.

Ores can be easily found in caves, since caves are already hollowed out, while you need to mine all the stone to get the ores when you strip mine. if you can't find any caves or you only strip-mine, then try to go to level 10 to find good ores. When you end up in a cave, try to explore it, you can find lots of ores in caves.

For transportation, I recommend you use minecarts, as minecarts can let you get around fast, and does not waste your hunger bar. If you are unable to get get or use minecarts, you can dig a very deep hole with water on the bottom, making you fall in the water, so you don't take fall damage. To get back up, make a water elevator with soul sand at the bottom, as the soul sand will cause you to go launching up to the top at a very fast speed.

As of the most recent 1.17 snapshot, caves have increased in size, length, and complexity, and diamonds now have "reduced air exposure". The best way to search for diamonds is now to go as low as possible (near y = -64), and go swimming in the new giant underground lake caves, as they have large amounts of exposed diamond even compared to the cave walls.

A good way to mine fast is by using a Haste II beacon combined with a Efficiency V Diamond or Netherite Pickaxe or some of the above answers are useful too