Saxa -
I also have Speedplay Frogs. Before that I rode with toe-clips for years and years.

I practiced (walked my bike there!) on a school track for hours before I ever rode on cement, even a parking lot! I clipped in and out as I rode, pedalled with one foot, pedalled with a clipped-out foot using my arch, practiced stopping and starting. Once I felt like I was getting bored with the track, I took it onto the grass.

Lemme tell ya, after clpping in and out on the fly and pedalling with one foot and pedalling with one clipped and one not-clipped IN THE GRASS, the whole deal got easier.

Can you find a track or field where you can do circus tricks until you've mastered the pedals?

In hairy looking situations (stop signs, hills with sharp corners, small children on the bike path) I always clip out one foot and pedal with the arch. Just in case I have to stop sooner than I expect.