Check on the Health and Well Being of You and Your Passengers
See if everyone in your vehicle is safe and not injured. Make sure to look at each person, look at their eyes and see if they are "shocky" and that they are responsive. If you have any question about their well being, contact 911.
Grab a Pad and Pen and Your Car's Information
Get out of the car with a pad, pen and your vehicles information. You need to have handy your license, Vehicle registration, and of course your insurance card. Before even leaving the car, jot down the license plate, make and model of the car that hit you, just in case he tries to run off. (Hit and Run).
Keep Your Temper
No matter how stupid or angry the other driver may be, keep your cool. Do not trade barbs do not answer stupid questions like "what were you looking at" or "Didn't you see the stop sign." The other driver may be trying to get you to say something that may hurt you in court later. Just say to the other guy, "I have my information, would you please let me have yours." If you meet with resistance or a continued belligerency, Get back in your car and call 911. Lock yourself in. Do not feed or otherwise deal with the other guys road rage. Do not exhibit your own road rage. It will be a lot better when witnesses report that he was a raging lunatic and you acted in a thoughtful and reasonable manner.
Information You Need
You should get his License number , address, registration and name of the registrant (it might not be the same as the driver's) and insurance company name and telephone number as well as the insurance policy number and date of expiration. If any of this information is expired, CALL 911. A driver must have a car that is properly insured. registered and he must be licensed. If he only has expired information, he may not be in compliance and may be (and probably is) committing a crime. Do not let him leave until the police arrive. Get his telephone number and the names and if possible the addresses of anyone in his vehicle. If their are witnesses (not in the cars but strangers on the street) get names phone and addresses.
Go Back to Your Vehicle and Begin Making Notes of Your Own
After you have obtained information, go back into your vehicle. Write down everything you observed. Describe what if any wounds you saw or heard others complain about. Describe the damage to both cars and draw pictures to help you remember. You do not have to do a Rembrandt worthy depiction. If you have a camera, take pictures. If not get one later and take pictures as soon as you can as is practical.
Call Your Lawyer or Insurance Agent
Contact your lawyer or Insurance agent. The latter will report the accident. The Lawyer will advise you to do so (more than likely) but if it is a minor accident that may not be in your best interest. Hence call your agent if the car is severely damaged or if anybody was injured enough to go to the hospital.
Remember Car Accidents Must Be Reported to DMV
The Dept of Motor Vehicles requires that a person in a car accident file with it a DMV 104 or report of accident. DO not delay filing this. Get to a lawyer and get this served. Likewise if there is municipal liability (ie traffic light was out etc.) Then you have to file a notice of claim (or notice of intent to file claim if you are suing NY State). Finally be sure if you or others were injured to contact your insurance agent to activate the under/uninsured drivers benefit. This payment will try to make up for what you lost by being fired etc.
In Conclusion, don't panic. It is a car accident, and if it did not result in your death then it is better than it could have been. Be thankful you are alive and hopefully not hurt too badly. Finally be sure to keep your information in a safe place, same with the information you gather. Report things promptly and only answer questions that are relevant to the exchange of information, otherwise do not talk and call your lawyer.