Complete Current Objective
First begin any goal, then pause hold L1 and enter Triangle, Right, Up, X, Right, Circle, Up, Triangle, Square, Left, Up, X. The pause menu will shake to confirm entry.
Kareem Campbell: Special Moves
Perform the following moves with a full meter:
B-Ballin Slide: Left, Right, Triangle
Double Blunt Slide: Down, Up, Triangle
Kickflip Backflip: Left, Down, Circle
Unlock Everything
First you need to be playing on the first level. Press pause and hold L1. Then press up, up, up, down, down, down, square, square, triangle, circle, up, up. Then complete one goal and exit the level. Save and restart the game and you will have everything unlocked.