do customers do and say that irritate car dealerships? The website Reddit asked car salespeople to weigh in on this. What's something you don't want customers to know when buying a car? What took place was a wide-ranging discussion on the frustrating and often intimidating process of negotiating for a new or used vehicle. Overall, the consensus was the same: People who do their research and come armed with information stand a much better chance at nabbing a great deal. And when you're negotiating on a car, one of the best advantages you have is patience.