If you are able, make sure to take pictures of the following:
1) Both cars with many different angles
2) The other person's driver's license
3) The other person's insurance information
4) Any injuries you or any of your passengers may have experienced
5) The surroundings like the intersection, stop lights or stop signs
6) Anything significant that could have contributed to the accident such as the angle of the sun, obstructions, or positions of cars.
By taking pictures, you can really add a lot to your case to prove that they were in the wrong. Without these your case will be much more difficult and may turn into a "he said she said" scenario. Pictures can be very convincing and dispel many ideas on what may have happened to cause the accident. Even pictures of things you don't consider relevant can be extremely important when building your case.