You know how to do a wheelie right, well if you don't you should probabley learn how to since this is the basi to most of your tricks.

Anyway what you need to learn is how to lift your back wheel off the ground. As you ride stand up on your pedals so that your cranks are horizontal. Then you twist your feet forward just a little bit and pull up your feet. That sould probably get your back wheel off the ground. Anyway when you marster that you just do a wheelie first and then pull up your back wheel as your in the air.