Codes
Enter the following codes at the "Press Start Screen" while holding down R1 & L1

Unlock All Characters
Circle, Triangle, Circle, Triangle, Circle, Down

Unlock All Sleds
Circle, Square, Circle, Square, Circle, Left

Unlock All Tracks
Circle, Left, Circle, Right, Circle, Up

Unlock Hover Sled
Circle, Triangle, Square, Circle, Triangle, Right

Unlock Everything
Circle, Square, Up, Circle, Triangle, Down

Rival challenge mode
Successfully complete the game in championship mode with any character to unlock rival challenge mode.

Black Diamond track
Win championship mode with any character to unlock the Black Diamond track.

Easy points for secret characters
Find a large ramp to do tricks off. Do a trick, then turn around and do it again. You can take as long as needed to build the points. Then, finish the race to unlock the secret character. This can be done on any track that you still need points for a secret character.

Losing sleds in rival challenge mode
Do not challenge a rival on a track that you cannot win. If you challenge a rival and lose to him or her, the sled you used will be lost and have to be unlocked in championship mode again.