Where is a good place to find dragons to kill?

The best way to find a dragon is at one of the many shout word altars. They appear as dragon heads on your map and compass. The easiest one I can tell you about is near Ivarstead. Just go south from there, and you will eventually get a dragon head icon to show up on your compass. Just go there, and you will meet a dragon, and get a new word for a shout.

You could also try fast travelling around as this is often a good way to invoke a dragon attack. Just travel to a location and see if there's a dragon around the place. If there is, great. If not, just travel to another location and repeat.

The best way to consistently locate dragons is to complete the Companions quest line. After finishing the quests 'Glory of the Dead' and 'Dragon Rising' you can approach Farkas or Vilkas and ask for work. They will then give you the radient quest 'Dragon Seekers'. This quest randomly selects from a list of Dragon Lairs and sends you to kill a levelled dragon there. You will find some nice loot and the quest giver will give you a levelled sum of gold. Unfortunately there is a bug associated with this quest where the dragons will occassionally not grant a soul, but you'll still get some loot and it can be repeated as needed.

You can also locate dragons by fast travelling across the map randomly, as they will often appear after fast travelling to a location. You can hop around the map until you find a dragon to fight, then repeat as needed. Could take quite some time as this is random.

See the list of all Dragon Lairs and their locations here (UESP Wiki). Note that (from the same link):

The dragons found at Dragon Lairs will always respawn, no matter how many times they are killed. This is an excellent way for any player with the skill to kill them to earn valuable experience and items and to test their combat prowess. It is especially helpful for lower to intermediate level players.

The radiant Companions quest, Dragon Seekers will have you killing dragons. This is also the case with one of the random radiant Bounty quests (a quest given by an innkeeper, jarl, or steward), and with the radiant Blades quest, Dragon Hunting.

Note that there is a bug regarding respawned dragons:

Respawned dragons found in previously cleared Lairs will not always give dragon souls.

This is fixed by the Unofficial Skyrim Patch (original / Legendary Edition - PC) / (Special Edition - PC) / (PS4) / (Xbox One) :

v1.0 - (2012-04-07): Fixed some encounter dragons not burning up nor giving the player a soul when slain (respawned dragons were not being properly reset)

Go to Dawnstar. There is almost always a dragon attacking Dawnstar.

Best way to find them is going to high Hrothgar and asking for a word of power location. Following that will mostly result in a new dragon camp. If not, just go wander between towns and do any camp that shows. You'll find a dragon camp eventually and if you have a few you can occasionally travel between them to find normal dragons.

I usually find some in the plains near Whiterun. They are also found around mountain-tops.

I finda a dragon almost every time I visit the Western Watchtower neer Whiterun after you go there with Irileth

Dawnstar has dragon attacks a lot, College of winterhold often has them, and dragon camps. If you go to Whiterun just keep talking to a gaurd until he mentions Shearpoint. Due to a glitch you can fast travel to shearpoint without discovering it. There is also a dragon preist at shearpoint that respawns (but his mask doesn't).

There are many places, Such as shearpoint Auntumwatchtower mount anthor and more. These places have a dragon head on it. There is a dragons lair where it usally will be. You can get shouts from dragon lairs. Shearpoint has a dragonpreist. Once you colect a dragon priests mask it starts a new quest. The masks are strong and have a special enchanment like stamina reloads 20% quicker. Dragons spawn everytime you are at its lair no matter how many times you kill it. So you can get its scales and bones and gold. Another place is bonestrewn crest. It is located south of windhelm. Thats it for now. Good luck killing your dragons!