Practice in quiet neighborhoods before you take your show on the road.

I agree with Kim about caged pedals. Especially if you're wearing sneakers - they can get caught in the cage when you're trying to get out of them.

When I got my first clipless pedals (back in the stone ages before "float") the bike shop put my bike on a trainer and I practiced clipping in & out over & over again. They also positioned the clip so that it was correct for my foot & pedal stroke. If you bike shop balks - put your hair up under your hat, swagger in, spit on the floor & scratch your crotch. They'll think you're a man & they'll take you seriously.

<was that out loud?>