Seek aid for any apparent injuries.
Call the police.
Notify security if the accident occurs on private property.
Give the authorities complete and accurate information.
Ask that a written report be made and get the report's identifying number.
Secure the names, addresses and driver's license numbers of other involved parties.
Get the other car's license number and state of issue.
Call your insurance agent and relay the pertinent information.
Discuss with your agent whether to file a claim through your own insurance company or pursue a liability claim against the other party.