The golden rule of all fender benders is to maintain your composure. It doesn't help the situation to argue, yell, threaten, or blame. Remember, your primary goal is to reach a settlement with the other driver or your insurance company so you can get your car fixed without digging into your own bank account.
You don't want to say anything that could interfere with the settlement process. So, it's best to be diplomatic and business-like. Simply inquire about the other driver's well-being, act polite, and keep calm--even if you're faced with a hostile and argumentative person.