These are a few suggestions for someone who has never tried flip turns, not rules written in stone and not for experienced turners.
A Few Don'ts:
1. Don't hold your breath going into the turn. Do exhale through your nose forcefully as you rotate. 2. Don't complicate the task by trying to place your feet on the wall. Do practice your turns in open water, far from the wall. 3. Don't try to twist into a freestyle position. Do come up completely on your back while you are learning. 4. Don't slow down before you flip. Your momentum will make the turn easier. 5. Don't flail your arms everywhere after you're over. This is a major problem for almost all new flippers because the correct arm position is counter-intuitive. When both your arms are at your side and you have not yet swung your legs over, your arms are already in their correct position facing the direction you want to go. You need only turn your hands from palms facing up to palms facing the bottom of the pool.
The Flip Turn, Simplified:
Swim fast. Simultaneously do three things, all quickly: tuck your chin to your chest while pulling your outstretched arm to your side (your other arm is at your other side already) and make a dolphin kick. Be patient and don't do anything else until you are folded in two with legs quite straight and eyes looking up to the surface of the water. Then, at the same time, turn your palms down and press on them while bending your legs and your turn is complete. Don't forget to leave your arms alone. It's your hips that leave your hands, not the other way around.
Check out these sites as well for more info on the flip-turn.
The Freestyle Flip Turn for Swimmers
Sorry, just noticed the links didn't post they are: