I usually stop behind the car's left rear wheel... because at stoplights there's usually a lot of oil/water on the road from the cars. The last thing you want is oily tires on the road.

If you live in a state that allows lane sharing/splitting... the best place to be is right on the dividing line between the cars if it's a 4 laner.

 

I know everyone has covered this, but for me each stop is different. I try to always at least be already headed for the best escape at the time. I Find my self in diferent postions at different times ready to take off. Every thing from weather to type of traffic influences this for me.

The one time I was almost rear ended, was the time I was not looking. I was at the stop sign he swerved and had to slam on his brakes next to me.