This ones quite hard to explain, so you may need to read over it a few times. Choose a 'medium to hard gear' (4th ish). Ride along slowly, pull a small endo, and when the back wheel comes down pull the front end up so you are in the same position as if you were wheelie-ing standing up, as the front wheel starts coming down, release your back brake and do a QUICK quarter pedal turn, while pulling the bike up (so you do a hop). While the bike is in the air, put the back brake back on and begin to 're-cock' the pedals, ready for another quarter pedal turn. When the bike lands, the front wheel should be pretty high again, when it starts to fall, do another quarter pedal turn and so on. Practice enough and pretty soon you should be able to do dropoffs by backhopping up to and over the edge.

[edit] See also

Bunnyhop