What to do if you are in an auto accident

Make sure any injured people receive proper medical care. If in doubt, call 911. Care in the first hours can be critical.
Write down the license plate numbers of ALL vehicles at the scene, including vehicles belonging to any witnesses. Note the make and model of each vehicle.
Notify police. If they respond, write down the case number and the officer's name.
Exchange contact and insurance information with all drivers involved. Write down the names of any passengers involved.
Ask any witnesses or bystanders for contact information.
Document the scene: draw a diagram and take pictures of the vehicles and damage. "A picture is worth a thousand words" and can show how the accident happened and the force of impact.
Report the accident to the State Department of Motor Vehicles.
Call an experienced personal injury attorney.
Call your insurance company.

Admit any fault or liability.
Blame the other driver, even if they were clearly at fault. After an accident, everyone is in shock and it is important to remain calm, assist any injured people, and stick to the facts. "Fault" is often a complicated legal issue and does not need to be allocated, or even discussed, immediately.
Give any statement to insurance adjusters before talking to an attorney.
Agree to any settlement before the full extent of your injuries, if any, is known.