Of course the first thing to do after a car accident is call the police. Call 911, get somebody out there to help investigate the accident and then document what happened. The next thing you should do is document the scene and take pictures of the vehicles, if there are skid marks, take pictures of those. If there are witnesses I would get their name, address, phone number — you can download the Herrman & Herrman app and it tells you everything to do on there.
You definitely want to exchange insurance information with the other driver, make sure he’s got good insurance, get his name and address. See if you can get him to admit fault, maybe you can record him on your app saying that he’s at fault. You want to gather all that kind of evidence.