What should I do after an accident? What information should I exchange?

State laws vary, but in general the steps to take after an accident include the following:
Stop at once.  Position your car so that you don’t needlessly block or endanger others. If you drive off from the scene, it will be considered a hit-and-run, which is a serious infraction in most states. 
Check to see if anyone is injured.  Some states require that you render reasonable aid if anyone is injured, but don’t do anything that could cause further injuries.
Call the police for a report.  Insurers like to have a police report if possible, and it’s required in many states.  If you have a minor parking lot accident, the police may not have time to come to the scene, but you will be able to tell your insurer that you did make the call.
Exchange information.  The basic rule of thumb is to exchange the following information with the other driver:
  • Name
  • Name of the owner if not the same as the driver
  • Names of any passengers
  • Vehicle’s make, model and license plate number
  • Insurance information – company name, policy number and phone number to call for claims
You are not required to show your driver's license, proof of insurance or your contact information to anyone but the police. You do not need to ask for that information from anyone else.
We’d also suggest that you:
Find witnesses.  Get their names and phone numbers.  Encourage them to stay until law enforcement comes so that their statements can be taken down. Independent witnesses tend to give an unbiased description of how the accident happened, which insurance companies like.
Take pictures. If possible, take photos of the damage to each car and the whole accident scene.  If you have a phone that takes good-quality pictures, use it. If you don’t, keep a digital camera in the glove box.  A picture can be worth a thousand words when making an insurance claim.
Check with your department of motor vehicles (DMV) to find out what’s required after an accident. Some states require an accident report if there are any injuries and/or property damage over a certain monetary threshold.