In addition to verifying the paperwork, I also take a full set of pictures before and after returning rental vehicles as evidence of the condition they are in.

Enterprise attempted to file a claim against my insurance for damage they stated happened while it was in my possession. In reality, I had returned the vehicle in pristine condition that morning and there was a minor hail storm that swept through the area that evening which damaged all the vehicles parked in the lot. It was pretty easy to see what had actually happened and I told them I was taking photographs and was prepared to sue them if they filed a fraudulent claim against my insurance. They backed down but I will never rent from that company again.

Weirdly enough, I've never had any problems with Hertz.