Hardly seems necessary for a tutorial on this one - but just incase you're simply playing this for the gamerscore and know nothing about skating - basically do a kickflip (or heelflip - find instructions in tutorials in the start menu) in the general direction of a ledge or a rail. When near the ledge or rail, hold one of your sticks in any direction.
You can set a respawn marker with DOWN on the D-pad, and you can spawn at this marker with UP on the D-pad. Keep trying and eventually you will unlock this achievement.
Here's a video I did showing how I unlocked this one - this will unlock with slides as well as grinds using the trucks: