All Bikes
Press Up, Left, Up, Down, Up, Right, Left, Right, Circle at the selection screen
All Styles
Press Left, Up, Right, Down, Left, Down, Right, Up, Left, Circle at the selection screen
Bonus Bike and Rider
Complete the game with any rider to unlock a bonus bike and Slim Jim
Extra Points
As the timer reaches Zero. Press X and bunny hop while not on any ramp. Hold Up + X or Down + X and you'll continue to get points even tho' the time has expired.
Tips/Hints
Grind my son...
If you're starting to fall sideways or near a wall/ledge, press triangle (The grind button) to attempt a grind. Thanks to the Dave Mirra Physics, you'll almost always magically hit the ledge... Much better than a crash isn't it?