The good news is this is somewhat Easy, the bad news you need a friend. Feel free to Add me on steam. You can find my profile at
http://steamcommunity.com/id/KinglinkAs for the achievement it's a little more complicated. You need to best a friend's score, then you go into the feat leaderboards (under your leaderboard screen on the minimap) and choose that feat, scroll down to the person you have bested (or tied) and it'll tell you how to call-out. On the xbox 360 controller it's the Y button.
Your friend MUST have played the game, MUST have recorded some score (any score) and you MUST be better or at the same level as that score. You can't call out people who have played the game but haven't recorded a score for that feat yet.