Learning hit jumps in the park
I am not nor do I intend to become a snowboarding instructor. These are simply the things that helped me teach myself how to jump as a park beginner. I just figured I would share my experiences in the hopes that it may help others.
First of all, start small. This seems obvious, but when you're in the park watching far better riders throw 720s and backflips, it's pretty easy to get sucked into or hype yourself into hitting something you're not ready for. All that is going to do is discourage you and possibly get you hurt. Just remember, those guys throwing those tricks that you (and I) hope to someday throw had to start out from somewhere too.
What I did was find a nice small jump and I didn't even fully tackle it at first. Get comfortable popping off the shoulder at a height of 2-3 feet, whatever you're comfortable with. Build you up some confidence doing this and once you're completely comfortable with that, then go ahead and hit the jump full on.
Now, when you're hitting the jump full on, realize that every being of your body is going to be telling you to face forward. You have to realize, you're sliding down a slope sideways and know you're about to be airborn. Your instincts will tell you to square your shoulders to the motion just like they did when you were first learning to ride. If you have an issue with this, point in the direction you're going, it'll help.
If you find yourself getting too much in the backseat and landing on the tail or losing balance and washing out on your heel edge on the landing, go for an indy grab. Going for indy grabs helped me more than anything. First of all, it gets your body weight going forward which keeps you from getting in the back seat. I think it also just helps give your conscious mind something to occupy itself with instead of screaming "Oh shit, we're in the air, what do we do?!" and trying to convince you to square your shoulders.
The last tip I have is to ride it out. I was washing out on some of my earlier attempts by trying to scrub speed immediately upon landing. Don't do that. Just ride it out and get stable before scrubbing speed.
These are some of the things I concentrated on doing and I went from popping off the shoulder of a jump like I described to hitting legitimate 20-25 footers in 3 days of riding. Now keep in mind, I was a solid intermediate rider, I had just never been in a park before. I was used to doing drops and hitting "jumps" on the slopes, but getting used to jumps with kick and the amount of air took some getting use to. I never felt the need to do a grab outside of the park, but I have found that grabs definitely help me stay more stable in the air.