i only learnt to do it about a week ago but hey,this is how i learnt i did it in a day, get up on your back wheel and wheelie forwards out of it a few times until you are comfortable with that. Then when you are on your back wheel put your break on and croutch down , then spring forwards at the same time as doing a quarter tern on your crank and letting go of your break.
hope this has helped :)