How to do a whip
1.Go like you would normaly hit a jump but be on the sides of your tires(so like on a lean)2.When you are just going off the jump you would want to twist your body to get the bike to go side ways, then lean to one side to get it to go on like a angle.
3.Then to get it to go back you would want to twist your body the oppisite way and the angle will go back strait to and you should have done a whip.
This is another way you can do a whip
http://www.youtube.com/watch?v=qqR6AEXwxoQ&feature=channel