Fast Start: 
As the "Go!" sign appears, press the A button. Your character should jump and go faster. 

All Tracks, Boards, and Characters: 
At the "Start" screen (where you can select Start, Lesson, or Option), press Analog Stick Down,
Analog Stick Up, D-pad Down, D-pad Up, C-DOWN, C-UP, L, R, Z, D-pad Left, C-RIGHT,
Analog Stick Up, B, D-pad Right, C-LEFT, and Start. If you've entered the code correctly, you'll
hear "Yeah!" and will start out with all the extra mountains, boards, and the hidden character 

Hidden Ninja Land Track: 
Earn Gold Cups on the first 8 tracks. The ending sequence will be displayed and Ninja Land (track
9) will now be open. 

Hidden Quicksand Valley Track: 
Earn Gold Cups on the first 6 tracks and you will be rewarded with Quicksand Valley and another
snowboard. 

Hidden Silver Mountain Track: 
Earn Gold Cups on the first 7 tracks and Silver Mountain will open up. 

Secret Character: 
Earn a Gold Cup on Ninja Land and you will get the secret character.