Best advice I can give is to do learn them off a jump/takeoff with no lip. Kinda like jumping off trail from a cat track. This way it really forces you to nollie; and if you're dropping into a steeper run, the fall doesn't hurt as much since its steep. A good trick to frontflips is to do a quick tailpress right before you start your nollie. It gets your body into a rocking motion and makes it feel more natural. And remember to suck your legs up once you take off! Good luck, let us know how it goes.