What is the best way to stop and restart at a stoplight?
These are the options I use depending on the circumstances:


Trackstand: Requires a lot of practice and it is a bit of a swhowoff. (This is the one I use the less)
Partially Dismount: Preferred when riding cleated pedals. Dominant foot stays on the pedal, and the pedal is kept ready for a full stroke (at 45 degrees over the horizontal as the other answer says). The other foot goes to the pavement. Preferred on busy crossings or when I have to use a lane not next to the curb.
Right foot on the curb: My Right foot is the dominant one, but when I get to stop besides a curb, the fact that I remain in the saddle almost makes up for having to take the first stroke with the left.
Use your hands: When there is a light pole or a suitable road sign, I keep mounted (and cleated) and use my hand to keep balance. Sometimes I can even put the shoulder against a pole or wall or the end of the handlebar. This one lets me re start fully engaged to pedals.