Shaun Palmer's Pro Snowboarder

Highlight the "Options" selection at the main menu. Then, hold R2 + Right and press Triangle, Square, Triangle, Circle, Triangle. Note: This also unlocks the two secret characters.

Hold Left + R1 and press Triangle, Triangle, Circle, Triangle.

Do like a flip just as you go in a snowmobile, truck, etc. It will still give you the flip and you will always land it.