seriously if you're just going up and sending it off a jump there's a pretty solid chance you'll get hurt. go find a trampoline somewhere and work them there.
as far as learning them on a trampoline, do a bunch of cork 7's where you come through to your butt/back. if you can do that and land on your back but with your body and 7, jump a little higher and send it, finishing a cork 7 early and then basically pulling your legs like you're trying to do a backflip. it won't come out like a backflip but if you pull it like one your cork 3 will come around.
seriously though, you might want to chill out on the 'just sending it on snow' part