This achievement isn't too bad. To get it, you'll need to complete the first mission and capture the first garrison. After that, find a dragon somewhere in the wild. You'll want to keep your distance and attack it from far away. As soon as you do, and it turns red, just crouch using B, and hide behind some cover, keeping your movement to a minimal. After a few seconds of searching, the dragon will turn yellow and then aqua/green. Once it does you should unlock the achievement.
Also, it is important to note that this achievement is a little weird. If the dragon begins to attack you, and you engage, the achievement may not unlock, but you should be able to gain the attention of the same dragon to try again.