Well I gotta say I would recomend trying them on water ramps first. The risk factor on that first one is pretty high. I'm glad I did water ramps first or I would have taken a huge fall and probably broken something.
The biggest piece of advice I can give you is to warm up with some big flat 3s, get the feel of that set solid. Then the jump before you go for the kang, do a straigh air and count to yourself in the air "1...2...switch". Get that rythm solid in your head so you can guage how fast to set. Keep that in your mind while your doing the trick to help keep you oriented, spot the landing as you come out of your first flip, but keep pulling it around smoothly. Spoting for your landing the second time is just like coming out of a rodeo 5 so that should feel familiar.
Good luck and post vids of ramping or if you decide to go for it on snow