You must stop. Someone could be injured and need your help.
If anyone is injured, call 911. Administer first aid to injured parties. (Not all traffic accidents require a police response. Most non-injury traffic accidents can be handled between the parties.)
If no one is injured or killed, move your vehicle out of the traffic lane.
Show your driver’s license, registration card and proof of insurance to the other driver or to a police officer. You are also required to provide your current residence address.
Get the facts. Write down the details at the scene:

• License plate numbers.
• Damage to all vehicles involved.
• Name(s) of other drivers, addresses and phone numbers.
• Insurance company names and policy numbers.
• Name(s) of all passengers, pedestrians or witnesses, addresses and phone numbers.
• When did the accident occur? Date and time.
• Where did the accident occur? Cross Streets and City.

If you have a camera, photographs can be helpful for future reference. Carefully choose a safe location from which to take the photographs.
If you are unable to locate the owner of a car or other property that you have collided with, you must leave a note secured attached to the property in a conspicuous place, which includes your name, address, and the name and address of the owner of the car you are driving.
You must also contact the local law enforcement agency.

Emergency Item Checklist:

• Pens/ pencils
• Camera
• Blanket
• First Aid Kit
• Jumper cables
• Flashlight
• Flares
• Paper/ notepad

References:
DMV driver’s handbook
AAA pamphlet: “Protect Yourself In Case Of An Accident”