When you go of any jump (Kicker, Superpipe, Cliff), hold L1 + L2 and press Left Analog-stick Left and a colored 'X' will appear. This indicates that you have executed the commands correctly. At the side of the screen where it tells you what tricks you have done, 'Special Bonus' will appear at the bottom. That special bonus will boost your score. You also can hold the correct buttons and keep pressing Left. If you end up near a grinding rail, hold Triangle. When you finish the grind, your score will easily be 3,000 points.