carve the way you want to spin/ pop / drop your shuoulder and let your feet come up with the rotation. feels pretty weird first couple of times but then you the hang of it. do whatever gra you want man.
doing them on tramp is hard, its easier on skis. come into the jump (carve a little if you feel comfortable with it) drop your inside shoulder alot and grap with your inner hand (it makes it easier). when setting the spin make sure the inside arm is lower than the outer one and look at the inside skis tails.
really what you should do is build a really fat jump into powder to learn, carving being the key to it. come in low and CARVE, drop your leading sholder and often times a leader safty helps bring it around, but critical and saftey will work as well.
I find you just have to really drop your left shoulder back if you are spinning left, and just kind of flow around that way and look at the ground, at 180 you should be looking down at the table, and then it kind of just comes around.