1. Call 911

The first thing to do is to call 911 to have police dispatched, as well as emergency services if someone is injured.

Even if it's just a fender-bender, "it's always good to have authorities on the scene to document and report what happened," says Anthony Noviello, assistant vice president in the claims division for Amica, based in Lincoln, R.I.

However, there are times when law enforcement won't respond. In bad winter weather, the police may respond only to accidents involving injuries, Bonelli says.

Police also may refuse to respond if an accident occurs on private property, like a mall parking lot, says Brandon Sutkowi, vice president at Meadowbrook Insurance Agency in Saginaw, Mich. If police are there, get the police report number, along with the officer's name and badge number.

2. Take photos of the vehicles and accident scene

Once you've called the authorities, it's time to start collecting key information related to the accident.

"The information that your insurer will need to investigate your claim is normally available at the accident scene," says William Brower, assistant vice president for claims for Boston-based Liberty Mutual Insurance. "However, it can be very time consuming to collect this information, if the details aren't captured at the accident scene."

Noviello recommends taking photos before the vehicles are moved to the side of the road. If the cars haven't been moved, the photos will document the point of impact between the vehicles. Photos should be forwarded to your car insurance company for claims purposes, he says.

3. Exchange personal and auto insurance information

Even if the police arrive, it's important to exchange personal and car insurance information with the other driver. Don't take the other driver's word about his or her car insurance provider. Instead, ask to see a copy of their insurance card, Bonelli says.

"There are situations where people make up information," such as when they are uninsured, Bonelli says.

Also ask to see their driver's license, and write down the information directly from that.

Brower says to take a close-up photo of the insurance information and driver's license. And Noviello says if the driver is not the owner of the vehicle, get the owner's information as well.

4. Gather information about the other vehicle

Write down information about the other vehicle, such as its make, model, color and license plate number. That's particularly crucial if it's a hit-and-run accident, Bonelli says. In that case, try to memorize the license plate number, or snap a photo with your phone.

The more information you can provide to authorities, the better.

5. Collect information from witnesses

Get the names, address and phone numbers of any witnesses to the accident. Those could be passing motorists or pedestrians or passengers in the other vehicle. Collecting such information can be especially helpful if you're involved in a hit-and-run accident. Witnesses may have caught the license plate number of the fleeing vehicle, Bonelli says.

6. Admit facts, not fault

Noviello cautions against admitting fault for the accident. However, you should tell police the facts.

If you spilled coffee on your lap before rear-ending the car in front of you, let the police know.

"You always want to tell the truth on what happened," Noviello says. Those facts are then used to determine fault and liability. Bonelli agrees that you should not comment about the accident unless answering questions from police. Otherwise, "you don't know how it could be misinterpreted."

7. Contact your car insurance company or agent

Depending on your insurer, you should contact either your car insurance company or your insurance agent. Amica, for example, sells its auto insurance directly to consumers, while others use agents to do so.

If you purchased your insurance policy through an agent and the accident happens after business hours, call the 800 number on your insurance card, Sutkowi says. Your insurer will want the “who, what, where and when” of the accident, as well as the number of the police report.

Noviello recommends calling your insurer "as soon as practical after an accident," because the sooner you call, the sooner the company can start processing the claim.