The key to a good backflip is you just need to have the balls and fully committ. I was about 14 or 15 when i landed my first 1 and b4 i landed 1, i landed on my stomach a couple times and on my head. Look for a jump with a really lippy takeoff and about a 15 ft gap (that is necessary for your first time). most jumps are built for spinning and have a more mellow takeoff. I was up at bear this past week and the two jumps at the bottom of black bear right next to the up rail would be your best bet for ur first flip. If ur regular stance, just committ and throw ur right shoulder down and your left shoulder up really hard. If you have the opportunity try it on a trampoline to get comfortable with the rotation. Its not a hard trick it just takes balls. Wear a helmet and goodluck.