Okay, IANAL, but here is what I know, from my experiences and some other peoples'. This is advice for minor fender-benders and bumper-kisses; If it's a 90 car pile-up, well, all bets are off.
Don't say anything ambiguous - When giving an offical statement, phrases like "I guess", "I'm not sure" or "maybe" are to be avoided. Either you are sure of what you know, or you don't know it. Yes or No. If a sentence requires you to add the phrase "...but I might be wrong..." on the end of it, it is better left unsaid.
Be Cooperative - I don't care if someone just totaled your Gold-Plated SuperCar, calm the fuck down. You are going to get nowhere by yelling and accusing. If the other party is clearly at fault, please resist the urge to insult their lineage and gentailia -- it will only make things worse for you. If one party becomes beligerent, the other party will get defensive, and then you have a less chance of resolving the issue like the opposable thumbed bipeds you are.
Drop your Ego - This goes well with the above element. You might think you're the worlds best driver, but if you just got in a traffic incident, there was a problem somewhere; you need to be open the fact that it just might, in some small way, be your fault. Automatically taking offense at everything said about you is a sure way if dragging things out for months.
Get Your Vehicle Towed Where You Want - In a road accident, it is vitally important for the roadway to be cleared as quickly as possible, so cars will often end up being towed immediately after the officers make their offical report. The problem here is that they will seldom ask you where you want the car towed *to*. Unless you specify a place for the car to be towed to, they will usually tow it to their lot and you will then be required to pay a storage fee, which can sometimes be in the hundreds-of-dolars (USD, of course). If you have the option, get them to tow it to your home, or a friends place, or anywhere that will not charge said fee.