Usually they just give you a good price.  Probably close to their best
price.  In one case when I did not respond for several days they sent me
another email with a slightly lower price a few days later.  That was the
best I could do on the car.

Not to split hairs here-- but one *negotiates* with someone you will have on
ongoing buy/sell relationship-- like with like the kid (or Mexican) who cuts
your lawn or the copy paper vendor in the office.

A one-time shot like a car purchase is called *bargaining*  -- maybe like
with a hooker in a hotel bar. Different parameters and strategies work
better in each kind of situation ;-)

I hate the back and forth dealing bit. They just try to wear you down.
For many years I've used this technique:
After looking around, including on the net recently, I come up with my
best value price for what I want. Research on prices is very important.

Then I go to the dealer(s) I'm interested in, state what vehicle I want
and say this:
"There will be only two  prices quoted, one by you and one by me.
You chose who goes first. If we don't agree on a deal I'm gone"

This approach has worked for me for years. Usually they go first and if
they are a bit high I quote my lower price.  Sometimes they will only do
the deal if I purchase some option, so far it was an extra I wanted.

Then after the deal is agreed on, don't suck into their very high cost  
special stuff, such as permanent wax, undercoating, anti stain on the
seats and extended warranty.  If you want those buy them outside the
dealer.

If a dealer gets nasty about my approach I leave immediately because he
has demonstrated he's not one I want to deal with.
Fortunately we live in a major city with lots of dealers.