I pretty much agree with what Soap said on this.
I've always said there are two steps to getting the best deal;
1) Know The Best Price - This means you need to research to know
what the best price actually is, what is the lowest price it can be purchased
for & best terms.
2) Demand The Best Price - This simply means you won't settle for anything
less than the best price (see #1). It does mean that you're willing to walk.
The first one who gives in, losses.
If I had to buy a car from a dealership (and I normally wouldn't),
I would walk in, hand the sales rep a paper with my offer for the
car I wanted along with my contact info & tell him.....
"I'm shopping several dealerships for this vehicle & the first one that
confirms this offer wins - I buy". Then promptly walk out.
Many dealerships will attempt to keep you at the dealership as long as they can,
for two reasons, one if you spend all your time there, you can't go anywhere else.
And two, it will wear you out & tire you to the point "you'll just want to get it over with".