For some reason I usually start on the right side of the hood, then the left, pass. fender, pass. door, pass. roof, rear end, and then drivers side, and front bumper. I don't have any reasoning, it's just what works with me.
I did my car the other day for the first time completely. I actually started on the front passanger door, and worked around the front - drivers side - back - and back to the passanger side. I figured that would break up sitting/standing in any one position for too long and would be more comfortable.