whoa whoa, this is some bad advice in this thread. i doubt some of these kids can do 7's.
a 7 is NOT like a 5 with an extra 180. this is a bad way to think about it, and will usually get you a 630 to death. get on a trampoline and practice just doing 7's and spotting your landing once at 3 and then again at 7. on snow get comfortable throwing 3's and 5's over about a 40 footer, then just go for it, but commit to doing a full 720, not a 540 and just trying to bring the last 180 around with your hips. make sure to spot that landing at 3, then when you come around at about 630 or so, pick it up again and put your feet on it.