Get Medical Care
If you're able, call 911 and make sure everybody involved receives needed medical attention from trained professionals.
Notify the Police
Call the police. It's a mistake to assume that "everything will work out" or that the driver who now assumes liability will later tell the same story to his/her insurance company. Police officers are trained to document the crash and to take statements from those involved. This is critical information when it comes time to figure out what actually happened.
Get information from the other driver(s). Note their name(s), address(es), phone number(s), and drivers license number(s) as well as their insurance carrier(s) and policy number(s). Get information from the police officer(s). Note their name(s), badge number(s), and write down the police report number. Get information from any witness(es). Note their name(s) and contact information--do this quickly as many witnesses will leave after making sure everyone is "okay."
Almost everbody has a cell phone with at least a decent camera. If you can, and if its safe, take pictures of everything. Pictures of the damage and position of the vehicles before they are moved can be very important. If you are not able to take pictures, ask a passenger or independent witness to do it for you. But again, this should only be done if they can do so safely. After you get home, take pictures of your injuries as well, including any bruises, cuts, or bandages/casts. Back-up these pictures so they are protected in case something happens to the originals.
Do Not Discuss Fault
If you were at fault, or if you think you may have been at fault, don't make any statements or say anything that could be taken as an admission of fault. Even if the other driver admits fault, don't discuss it, it may lead to an argument. You should however speak honestly with police officers and your OWN insurance company describing exactly what happened.
As soon as you are able, write down everything you remember. Document what happened, the road conditions, what was said afterward, whether any citations were issued and what injuries, if any, were sustained by those involved. Put these notes, along with all the information you gathered, in a folder so you can keep everything in the same place. Draw a sketch or diagram of the crash scene. It may be months, or years, before the crash is fully resolved.
Call Your Insurance Agent
All insurance policies require that you notify your insurance company that you were involved in a crash. Do this soon, the day of or the following day, or on Monday if the crash happened on the weekend.
Add to your Notes
Over the next several days and weeks you will likely make several phone calls and/or exchange several e-mails. Document everything taking note of who said what and the dates and times it was said. Remember to not discuss fault with anyone--especially the other party(ies) insurance representatives. Take notes on any medical care you receive including dates and doctor's names and the care you received.
Call a Personal Injury Attorney
You need to protect your rights. Unlike many people, personal injury attorneys dedicate their professional lives to working against insurance companies and protecting the rights of injured victims. An attorney who focuses his or her practice in personal injury law is best able to evaluate what needs to be done to get you fully compensated and best protect your interests. Most personal injury attorneys offer free initial consultations.
Everything you do and everything you say (including what is said/posted on Facebook, MySpace, Twitter, etc.) can come back to haunt you later--even if you think it was said in confidence or posted on a private social media account. If you really feel the need to post things, keep your posts honest and factual, avoid embellishing or being flippant or flowery in your crash-related posts.