Backwards somersaults:
Whilst you are setting the angle of jump (ie. whilst pressing B), tap down-up, then jump off at 60 degrees.
Increase distance:
Hack the run buttons whilst in flight to increase distance.
Mogule Jump:
Same as 'backwards somersaults', except tap left-right.
Super V Gliding:
Tap right-left BEFORE you set the angle of jump.
Speed up:
You could increase the speed even further by
bashing the d-button as well.
Forward roll:
During the announcement of your name, tap up-down-left-right-B.
Side roll:
Same as above, except tap the code backwards.