If you have just been in a car accident, it is likely that there are a million thoughts running through your mind and a million emotions racing through your body. It is in these tense moments immediately after a crash -- when you're stunned, angry, in pain and everything in between -- that you need to take a deep breath and prepare yourself for the next few moments in your life.
That deep breath is the first important step to take. Staying calm and being as cool-headed as you can possibly be (given the context) is imperative. If you aren't calm, you may get angry and lash out at other people involved in the crash. This will only escalate the tension of the situation, and that won't help anyone.
Once you are calm, go check on the other people involved in the car accident. Are they alright? Do they need assistance, medical or otherwise? Provide any help you can, and once the situation is stable, you can move on to some other steps, such as collecting evidence.
Yes, even you can be your own investigator. In the moments immediately after a crash, the accident scene is fresh and you can preserve that evidence by doing some simple things. You can take out your cellphone and snap a few pictures of the scene, the vehicles involved and the setting of the accident (the intersection, road signs, etc.). You can talk to witnesses and ask them if they will go on record with what they saw. You should exchange information with the other people involved in the crash and also contact your insurance provider.
Ultimately, checking in with a personal injury attorney to understand your legal situation is a good idea too, especially if negligence or great harm was involved in the car accident.