First, unlock CliffDiver, then go to the island that is on the straightaway to the Start checkpoint. You can get up the island by pushing down and throttle. You will slowly acsend to the top, when you get there, back up as far as you can without falling down. On the top, press turbo, you will fly off the island into the air, if you are good, you might be able to pull off three complete flips, and will get a lot of applause. happy flipping!