james has the right idea as far as commiting fully..
when i learned em I did the flip but wasn't thinking and let go of my scooter. it bent the fork so much that i couldn't ride til i got a new one (not worth it, ruined the rest of the day). so HOLD ON TO YOUR BARS.
secondly you want to just look straight back, its easy to say but harder to do. if you hesitate or dont put your head straight BACK you'll look to the side or start spinning funny and it'll mess you up.
takeway is:
consciously think about HOLDING ONTO YOUR BARS and then LOOK STRAIGHT BACK. don't turn your head or look over your shoulder, just straight back. then commit and you're golden. you'll guage how much you need to tuck into it or loosen up if you're over/under rotating. but thats the easiest best advice i can give ya if you remember just those two things. everybody else is right too ^^