When you approach a ramp, get enough speed up and once you have jumped off it, hold Triangle for a Powerdow. You can actually pull it off in midair and land it by releasing Triangle before you land. You can also do this with a Surfing Powerdown, but you have to release the trick button and Triangle to land it properly, or you will crash. You can also Powerdown onto a ramp and do a rotation trick on it. Note: You do not get any extra points for doing a trick in midair, just for the jump distance.