This game is also available on PS3.
If you can't get the height needed for a 540 spin, triple flips will also trip up your computer opponents. These require you to flick and hold a kickflip, allowing the board to spin multiple times before you land.
Also, adding a footplant upon landing, then continuing to spin will cause the spin to add up. Spin 360 degrees, footplant, and spin 180 degrees and you'll have an unstoppable 540.
Press and hold the 'world grab' button (same button for handplants and grabbing objects) to hitch a ride onto the back bumper of cars. You can grab onto them at a stop light or a stop sign or cars will also slow down when you swing in behind them (while holding down the world grab button) when you have some speed.
Once you grab on, the cars will start to speed. However, they still have to obey the rules of the road and they might get stuck behind a slower car ahead or stop at a light. So, keep your eyes on what is happening ahead and be ready to let go. When you let go from the side, hanging on with one hand, you pull yourself forward for an extra boost. Make McFly proud and watch for sports cars, they drive faster.