^Agreed 100%.  I learned to backflip offtrail at whistler 3 years ago.  Just remember to tuck your legs.  Find a good jump, not too large, with lots of softies for the landing, def. not a park kicker.  Lean back, but dont yank your head back, torques your body too much.  Then tuck.  Thats about it, I think its more natural then spinning.
Side note: Hit the jump a few times...my little bro destroyed his shoulder at 7 springs on a park kicker...hit the jump for the first time, over rotated, over shot the landing, and had to have two surgeries, and now has a 6 inch titanium rod straight thru the top of his shoulder into his arm.  Not to scare you, but you can fuck yourself if your not safe!