Stay calm. Remember that neither of you planned for this to happen. Gather your composure and feel good knowing that you have everything you need if an accident happens: cell phone, camera, pen, accident form, insurance, safety kit, cones or flares, flashlight and medical card.
Clear the roadway. If no one is hurt and the cars are driveable, drive off the roadway. Other drivers will appreciate you for this, and so will emergency workers. If the cars are not driveable, you are now a potential hazard to yourself and other drivers. Put your hazard lights on, remain in the car with your seatbelt fastened and call 911 for help.
Look around. Be aware of oncoming and passing cars. When safe, get out of the car, stay out of the street and set out cones or flares to warn other cars of the accident.
Exchange information with the other driver. Document the following information: driver's name, address, telephone number, insurance company, policy number, car make, car model, car color, license plate number, time of accident and place of accident. Take photos of the car damage and get contact information for any witnesses. These will be vital in the event there is a dispute as to who is responsible.
Call 911 or not? Since we're dealing with minor car accidents here, it is unlikely that law enforcement will show up unless injuries are sustained. When all information is exchanged and cars are drivable, get back in the car, watch for traffic and safely re-enter the roadway.