[Scott Douglas]

Know what you are looking for, not what they are trying to sell you. If a car 'isn't the one' exactly walk away.
Let the sales guy know up front that you have your own financing and are willing to buy 'the one' right now. And know what you are willing to pay for it too.

I once had a customer come into the Acura place on a rainy Dec night, close to Xmas. He told me he and his wife had been out drinking and stopped by to look at new cars as they were going to get one when they came back from their vacation in January. He asked for a brochure. When I got the brochure from the manager's office, the manager asked me what was going on. I told him they wanted to look at the brochure. He said to let them test drive the car. I thought is this guy nuts? They've admitted to me they'd been drinking, it's raining and he wants me to let them test drive a car?
Needless to say, they didn't test drive a car, but, the manager sicked the slimiest sales guy in the place on them. When this happened, the customer says to the manager "I thought I was dealing with Scott on this." Manager says, no, so-and-so is taking over.
They hammered this guy for 2 hours. He wanted to lease it, no money out of pocket, no money down type of thing. He really didn't want a new car sitting in his garage for 2 months while he was on vacation so he raked them over the coals for an outrageous deal he knew they couldn't do. We finally closed up for the night with them still at the table. Next day I walked in and quit. I asked the manager if he knew why the guy didn't buy a car that night. He said he couldn't do the deal. I told him no, it's because he didn't want a new car sitting for 2 months while he was on vacation. He asked how I knew this. I said because I talked to the guy.

So, the best advice I can give you is, be ready to walk out. There are too many cars out there not to be able to find 'the one' for you someplace else.