If you are physically able to do so then it is important to take care of the following things at the scene of the accident:
Call the police.
If anyone is hurt or you are blocking a major road then call 911. Otherwise, you can call a local number.
Get contact information for the other driver(s) involved.
This should include name, number, address, license plate number, and the name of the insurance company.
Take pictures of the accident scene.
If possible, do this before cars are moved from the point of impact.