This glitch will unlock Sick Highscore Achievement and of course That Combo Was Sick Achievement. It allows you to hang in the air, and you can do any trick without bailing, generating a lot of combos!
The glitch is on a white wall and located between Suburbia and Main Street areas of the map. You must be in Free Skate and in a session for the achievements to unlock. It can be a little tricky to find the right sweet spot for the glitch to occur. I have included a video from YouTube of someone actually doing it.
Doing grabs while rotating horizontally and vertically at the same time really increases your score. To exit this glitch, you need to leave your board (LB + RB).
Glitches That Unlock Achievements 