If you are involved in a car accident, as soon as you have secured your safety, record the license plate number of the other vehicle(s). This weekend, we happened upon an accident almost immediately after it had occurred. It looked like a Honda Civic rice burner had rear-ended a Ford Ranger pickup at a traffic light. The pickup pulled to the side out of the way of traffic and its occupants were getting out when the Civic took off. We were driving past as the Civic fled, so we memorized its plate number. We circled back to tell the people who had been hit, but in the minute it took to turn around, they had already left. I called the police department's main switchboard to report this, but they were closed, and I wasn't about to dial 911. Austin has a 311 service for non-emergency calls, but I couldn't get through. I mention this only to demonstrate that I attempted to fulfill my civic duty to the extent reasonable.
Incidentally, I had a "Rain Man" moment a couple of weeks ago. It appears that standard, non-vanity Texas license plates have a pattern. Cars are always Letter Number Number Letter Letter Letter. Trucks follow a different pattern, which I think is Number Number Letter Letter Number. So there you go. Make good use of that information.