i have taught swam for 22 years competitvely. what purpose do you want to do flip turns? i.e. training for a tri or just aerobic exercise. in any case to answer your question there are a few things needed to effectively do a flip turn.

1) swim harder into the wall (the momentum actually makes it easy to get your feet from behind you to in front of you on the wall.

2) keep your chin to your chest until you get both feet on the wall.

3) cheat, but recommend, when arms are at your side, push water with your hands up toward your shoulders and over them. (like hurling a big rock and throwing it over your shoulder behind you)

4) of course you core plays the most critical role. Tighten those abs and get into a ball while your arms are doing step 3

5) remember, it doesnt matter what side you turn to.

6) always remember to in that ball coiled up until you know your head is pointing to the other end of the pool and your feet are near the wall. Take your time to get those feet on then push off. Just be patient. it takes much repetition.

Hope this helps.