Cornering
When adjusting your character's stats, pay special attention to cornering; slaloming is the easiest way to lose a good lead.
POV
While it's easy to skip past them, replays can offer invaluable info about the courses that you won't see from your third-person POV.
Hard Turns
Use hard turns sparingly (L1 and R1); although they are necessary in spots, too many can blow your course time in the space of a few seconds.
Play as Mr. Chicken
Successfully complete all ten courses on any stage with all five standard characters using the same saved game file to unlock Mr. Chicken as a playable character.
Game music
Play track two and higher of the game disc in an audio CD player to hear music from the game.