How do I lubricate my chain?

Clean the chain first - see this question or this question.

If the chain has a master link I like to start there just so I can keep track of which links I have lubed easier.

Usually you should shake up the lube, especially if it is a 'dry' or 'wax' formula. Then drip 1 or 2 drops on the rollers of each link. Lube on the outside of the chain is basically worthless unless you are applying a 'wet' lube for weather protection. More than one or two drops on each link will be too much, and will drip a lot of lube onto the floor or ground where you are working.

Pedal the chain backwards and get every link. When done run the chain through all the gears. Let the chain sit for a few minutes then using a clean, dry, lint-free cloth, wipe the excess from the chain, cogs and chain rings.

You need to clean your chain and drive components first. Otherwise just adding lube will only provide minimal benefits. It might even cause more problems as excessive lube attracts more dirt.

The only time I may consider just applying lube by itself is if I just rode through some rain. In that case, I will wipe the chain with a rag, add 1 drop of lube per link, and shift through the gears to spread the lube around.

I recommend picking a certain number of miles to do your chain service like 100 to 200 depending on the lube you use. Obviously, it is better to do it on the more frequent side of things to prevent wear and tear, but there is no reason to go overboard on it (e.g. after a 20 mile ride in good weather/conditions).

The only time I use a visual indicator to determine when to clean the chain is if I am trying out a new lube. In that case, I look for the lube drying out or caking up and I listen for the chain and drive to start squeaking. Once I know what the real life of the lube is based on how and where I ride, I default to doing maintenance based on mileage. It just takes the guess work out of it.

Here is quick drive service that I do 100-200 miles depending on the conditions and lube used.

The steps I use when cleaning components are summarized as:

1. Shift Into the Big Chain Ring and Small Gear in the back
2. Degrease - Chain clean tools made by Park or Finish Line make things easier here.
3. Water Rinse Chain - Chain clean tools made by Park or Finish Line make things easier here.
4. Wipe Chain With Rag
5. Clean Drive Components (i.e. Cassette, Chain Ring, and Derailleur)
6. Clean Cassette (See Above) - Something like a rag wrapped around something thin and solid like a CD works well for me and is inexpensive. A example is shown here in this clip:
7. Wipe Chain With Rag
8. Lube Chain - Only 1 small drop of lube per link. Find the masterlink/quicklink on the chain and use that as a reference to make sure you only lube a link 1 time. Less is more here as unnecessary lube just flings off the chain onto your wheel or braking surfaces and attracts more dust. Some people like to wipe their chain after lubing it, but I have had good luck just sparingly applying the lube to begin with so that after the next step there is not much need to wipe any excess. However, again each person may have their own opinion or preference on the matter. I have had good experience with WD40 Wet Lube (Not regular WD40) and Finish Line Ceramic Wet Lube. I am sure each person will have their own preferences like people do when it comes to motor oil.
9. Shift through all gears and chainrings to spread the lube around.

You can spend more time cleaning components, by removing the wheel & cassette, but usually what is shown outlined above is sufficient to keep things clean for most people.

Hope that helps