The Heli is not a new trick. But it's still fresh, maybe now more than ever.
Completing a 360 is unfortunately harder than it looks, but what can you do? It's such a heck of a crowd pleaser. You know that you just have to do it. Before your skis come on, be sure to have completed at least one hundred 360's on your living room floor. When confidence is up high and the feeling of correctness in your mind is right, first, it's time for snow. Start up in a table top jump which reduces speed, this helps you keep balance and makes the landing somewhat easier.
1. Enter the jump knees softly bent. On kick-off point jump by extending your legs and hips to get the right balance and height. Back weight is a killer and not having enough height is devastating, meaning you will not have time to complete your rotation and might land backwards. (Though this could be done, I've never considered this on telemark skis 'cus the bindings tend to get a bit wobbly)
2. Create rotation by moving one arm forward - up from the hip, cross diagonal over your skis, pointing your right arm forward to your left (if clockwise rotation) and looking over your shoulder.
3. Get a feeling for how much rotation is required, control it by extending or contracting your arms. (i.e. - not enough rotation, contract arms. - to much, extend arms.)
4. Staying in a straight up position is super nice, looks like you're in extreme control over the situation. Be sure to stay extended in the hips, knees and back to avoid a sloppy position. Clean and cool. When this is mastered, try adding something to your jump like a different rotation, rolling, or going into a position (for example to a mute grab or an iron cross).
5. When you're closing in on a full lap, start taking your raised arm down (and let go of any resumed positions), to slow rotation speed.
6. Start looking for landing and spot your point of impact.
7. Focus on the landing, extend or raise arms to the side and spread your feet if necessary for stopping rotation.
8. In the moment of impact, put arms forward to reduce the possibility of getting back weight on your skis (i.e. landing on yer ass)
9. Keep skiing like nothing ever happened, that this was a most routine and almost obligatory jump, and collect the ovations from your crowd.
Do it, and do it again. There is nothing like practice.