A lot, actually.
But let’s give a more detailed answer to the question posed in the title. After a car accident, many people think that there isn’t anything that you, the accident victim, can do. However, there are many proactive steps that you can take to protect yourself and the other people who were involved in the crash.
To begin, you need to make sure you are mentally and emotionally prepared to deal with the other drivers in the crash. Naturally, tensions will be high after a crash. But if you can take a deep breath and remain calm, dealing with other drivers and people after the wreck will be easier.
Sometimes, though, other people in the crash won’t even be able to have these discussions because they have been severely injured. In these cases, you need to check on them and call 911 if they are in need of assistance. Provide any medical help you can and listen to the instructions of the 911 operator on the phone.
Now, if such drastic circumstances aren’t involved, or if you have completed any help that you could provide, then you can move on to documenting the scene in your own way. Become a sort of detective. Take photos of the accident scene. Capture images that show the intersection it happened at, or the street signs visible at the scene. Show the damage done to the vehicles. Also, if there were witnesses to the wreck, you can talk to them and see if they are willing to put their account of the crash on record.