All of what dirtygirl said with one clarification that helped me a lot, even though I'm not super good at wheelies.

The pull up that worked for me is more like a row. The muscles involved are my lats, so think of doing a row with bent elbows, and pull your elbows back. Before that, every time I tried my arms were totally straight and it didn't work at all....bend the elbows and pull your elbows back, along with the right pedal placement, right gear ratio, right timing of the pedal stroke, and voila! The front wheel is in the air!

Good luck and happy practicing!
~T~