Everybody seems to have there own method and I imagine that what works for you is the way you should do it.

For me, as I am coasting to a stop I unclip my left foot first at the 12 o'clock position. This just feels natural for me. If I'm waiting for a light I leave my right foot clipped and move it to about 1 or 2 for a good start. I have tried different pedal positions and both feet but this way just feels right to me.

When I first went clipless I leaned against a wall and practiced with both feet. That helped but I still fell a few times while riding until I got the hang of it.