I'd also agree with Irulan, practice on the grass. If you're still having problems then maybe try mountain bike-style cleats, like SPD or SPD-compatible. I've used SPD road and mountain, Egg Beaters, and Time ATACs, and LOVE the Egg Beaters.

Also shoe fit and shoe stiffness could be factors affecting your ability to clip out....

But don't go back to platforms and toe cages! Once you get used to clipless, you'll love them.

(BTW, if you are interested in the Time's, I have a pair of the ATAC carbon, with cleats, that I will either sell very cheaply or give away to a good home. They're almost new, but I never found clipping in very easy, and clipping out was a little weird too. But some people love em.)