either way, on land or on snowboard, you have to fully commit to it. if you half ass it, your gonna have a bad time. possibly land on your head. if you feel sketchy then don't do it.
You're gonna feel sketched out about it once it pops up in your head and you're staring at the jump.
Wildcat - cartwheel style. Dump your hip and your shoulder hard over your tail. Easy to get a fast flip, can be stylish with a fs tweaked melon grab.
Layback - (Check out the link in my signature...thats a true backflip in my opinion) Same as a wild cat except you are staring in front of you and you gradually shift your weigh back up the jump then finally dump your back hip over your tail and look at the snow. Should feel like you quickly stretch out your side, then you kinda kick your tail out and float. All style in this one.
Backroll - Like the lay back, but instead of backflipping over your tail, you back flip over your heel edge. Way sketchier in my opinion because you have a good chance of initiating a slight spinning rotation AND you may not pop right thus landing on your tail in the landing.
I recommend doing backflips on jumps that you know that you can get a floaty 3 or a 540 off of. If I can 540 something without having to chuck too hard, I know I can backflip it. If you cant 3 with comfort, then dont backflip. Because that just states you aren't comfortable enough with a snowboard.
I highly reccomend doing wild cat flips at first, you will get a quicker rotation and you dont need a large sized jump. A lippy jump that only sends you 5' is perfect. Quick to build as well. If you're in the park, then it's all up to you, find something lippy because you'll have more success in initiating a comfortable flip. When doing you're approaching the jump, look forwards but lean back more and more as you ride up the jump and then mildly punch for your flip once you reach the lip. Its less strain and it is much safer than to immidiately throw your body right as you are almost off the jump, because you can easily flip too early or too late. Too early will result in hitting your head in the jump (which is rare), too late will result in under rotation and belly floppin/ smashing your head (belly flops are common to see, smashing your head doesnt have a lot of chance, but its probable)