Liberate an outpost without triggering an alarm.

This is best done on the first few Outposts you come across. Mainly because they're made of few guards and are easy pickings. To liberate an Outpost with any alerts you must take the stealth route to killing everyone. You'll need to make sure the enemy AI does not spot you and this is pointed out by the white arrow at the top of your screen. If this fills up all the way to the sides and guard starts to shout and shoot at you, you've been spotted. This also counts if the alarm is set off.

The first thing to go is to find an advantage point near the Outpost and use your camera to tag all the AI in the area. This way you can keep track of them all. Once that's done, make your way around it distracting each guy with your rocks one-by-one. When they get close, either make sure you're hiding in some bushes or on a corner and press RS to do a takedown.

Using your gun should be out of the picture here, as it'll alert more guards to your spot. Just take your time and this should be quite easy. If by chance you have taken over all Outposts in the game but have not completed the Skills objectives. You can reset them all by going into the games options menu.