One rule I try to apply to myself at busy intersections: green doesn't mean go, green means look and make sure no one's running a red light, then go
especially at a light that just turned green, others trying to make it through yellow end up going through red and potentially killing others - I actually have my psychology students monitor different intersections in town to watch driving patterns (rolling stops at a stop sign, illegal turns on red lights, slowing vs. speeding on yellows, etc.) - its pretty interesting to see how few people actually consistently follow the rules of the road - yellow means speed up to most people, I've actually been honked at for slowing down!
we are starting to live in a society that is so technologically advanced that the humans in it can't keep up... cell phones, while awesome for an emergency (as ss3.0 said) are also about the easiest way to be distracted while driving, especially through text messaging, yet so many people do it. I hope someday we have cars that just automatically take us from a to b and take all the work and injury potential out of driving...it'd be fun to leave home, take a nap and end up at work with no fear of imminent death from the other robotic cars around us