The nine most terrifying words in the English language are, 'I'm from the government and I'm here to help.' - Ronald Reagan, 40th president of the U.S. (1911 - 2004)
I have purchased six cars in the last few years for family and friends, two new and the rest used. They entailed numerous dealer visits, test drives and taking the used ones for independent pre-purchase inspections. Only three salesmen asked for my driver's license. All were dissuaded.
There are too many dealers who want my business to make it an issue. If a dealer became obstreperous I would not hesitate to file formal complaints with all appropriate government agencies. It costs me nothing. It's like a 50-gallon enema for him. The pain never stops! Sane businessmen avoid civil servants.
I phone ahead and make an appointment, dress suitably and conduct myself in a pleasant, courteous and businesslike manner. Flexibility, honesty, mutual respect and patience lubricate a successful negotiation. Sales hustlers receive short shrift. I ensure the salesman has my contact information. I want him to follow-up with me.