Call 911 to report the accident and ask for an ambulance if appropriate.
When talking to the police, be accurate. Do not guess, and do not take the blame.
If the police do not arrive and gather information, then exchange names, contact information, and insurance information with all drivers. Get contact information for all witnesses (whether or not the police are investigating).
Take pictures (of the scene, damage, and injuries) if you are able to do so safely.
Get medical care for injuries, describing everything that hurts.
Report the accident to your own insurance company.
Call a personal injury attorney to protect your rights.