While in the air doing a trick, press the Print Screen button rapidly and you will get a lot of points.
NOTE: Remember to hold down the trick while pressing Print Screen but you still have to let go of the trick to land it!
Go to the end of the map where there is a BIG hill that goes straight up. Go a fair distance back and race full speed towards the hill. You should be able to make it up the hill. Once you're up, keep going forward and eventually you will be blown REALLY HIGH up in the sky. This can be done on any track except the supercross tracks.
Big Head Mode:
Type in "big heads" at the main menu.
Type in "kcussedocruoy" at the main menu.
Thanks to Revolution reader Michael and Tim Donovan!