Call the police before leaving the scene.
Take pictures of the scene as soon as you can.
When providing a statement to the responding officer, do not guess or attempt to reconstruct the chain of events. It’s OK to say “I’m not sure.”
Seek medical attention unless you are absolutely certain you are not injured. Head and spinal injuries can take hours or even days to become apparent. It’s always best to get checked out quickly.
Exchange information with the other driver.
Do not speak with representatives of the other driver’s insurance carrier. They do not have your interests in mind, and are instead looking for information to use against you.