I've walked out...just had to stop the dialog...the sales guy was trying way too hard...trying to get me into a payment when I told him 3 previous times don't worry about the payment...let's focus on the purchase price...they didn't have the car I wanted anyway.
I've learned to never get emotional...have a game plan as noted earlier and follow thru...a lot of times used cars (especially upscale certified pre-owned makes coming off lease from a bulk buyer) you can get the best deal on price.
Car sales could be an interesting study in psychology.
Car salesmen like to put you in "the box" for long periods of time and make you sweat it out. They are usually hanging out in the back laughing at what a sucker they got ready to hand them over a big fat commission. The box can be an office or just sitting out by yourself. I usually walk out. Then they are the ones sweating because they have to keep up with where I am or if I'm leaving. My favorite tactic is when they have to leave to talk to their sales manager, if they exist. They will also bring the manager into the box to explain why their price is fair. I doubt that this person is a manager at all. I stay firm with my price regardless, if there is no deal I want to hear it from them. I haven't heard a car salesman tell me that yet. They eventually come down to earth when they figure out they aren't dealing with an idiot.
I do a lot of research - It amazes me how much they don't know about what they are selling.
I make an offer, in writing and sign it. I'm not trying to fuck them over, the offer is fair and based on all the research that I do.
I stay firm on the offer - Think of Bernie Mac in Bad Santa
Me "31-5"
Them "38"
Me "31-5"
Them "36"
Me "31-5"
Them 35-5"
Me "31-5"
Them "33-250"
Me "31-5"
Them "We aren't off by that much"
ME "OK. Good. 31-5 and it's a deal."