This will be a repeat of what some others have said upthread, but here’s my thoughts:
-being predictive. Picking up on the subtle (and not-so-subtle) cues that tell you well ahead of time what’s going to unfold in the near future, giving you a comfortable amount of time to take action - more following distance, changing lanes, etc.
-being predictable. The more often you surprise other drivers, the more likely they are to misjudge something and make contact with you. Sudden lane changes or dramatic accel/decal means that the next time the other guy looks for you, you might be somewhere he wasn’t expected, and he may do something dangerous on the assumption that you are where he thought you were a moment ago.
-avoiding situations where others’ mistakes will cost you. Stay out of blind spots, for example. Leave plenty of following distance - not only to avoid rear-ending the guy in front of you, but so that you can decelerate gradually, thereby helping prevent the guy behind you from rear-ending you.
-Something taught to motorcyclists in formal training: separation of hazards. If you’re potentially facing multiple hazards at once, try to separate them out, e.g. change lanes after you pass through the intersection, not during.
-Making driving your primary task when you’re in the driver’s seat. Let conversations with your passengers become awkward if necessary while you focus on merging or changing lanes in heavy traffic. Gonna change songs on your MP3 player? Wait until you’re at a stop light, or at least until there are no cars or pedestrians anywhere near you.
-conducting post-incident analyses after an incident (“incident” here means crash or close call). Go through in your mind what happened, what you might have done that contributed to it, and - absolutely most important - what you could have done (and will do in the future) to improve the outcome, e.g. more following distance, slower speed, whatever. Consult your passengers (if any were with you) for their perspective). Establishing who had right-of-way in a multi-vehicle close call is less important, by far, than figuring out how you could have avoided that close call in the first place - even if it means surrendering your right-of-way.
A metric of an above-average driver (the outcome of all of the above) is a low rate of occurrence of close calls. The less often you are surprised or have to take emergency evasive action, or get a surge of adrenalin, the less likely you are to be involved in an accident in the future, and that also includes accidents that would not have been your fault.