Don't be impulsive. They will work the "drive it home today" game on you. Don't give in to it. I never buy the same day I walk in to look the first time. Not even the same week. But that is just me. I like to play hard to get and make *them* call *me* later on. You should also show that you are a serious buyer. Being pre-approved for loan helps establish that you are not tire kicking.
A lot depends on the market is it slow or are sales going well, and alot depends on the car is it an in-demand model or is it one they've had on the lot for awhile. Here's a tip: If you find a car you like, look on the manufacturer's placard on the door frame on the driver's side... the one that shows gross vehicle weight etc. It usually shows a build date in month/year format. That can be used to deduce how long they have had the car in inventory. The longer they have had it the better deal you may be able to negotiate. Or you can ask how long they've had it and they will tell you, but its still handy to see the build date on the placard.
you can usually get a slightly better deal on base trim models since they tend not to sell as quickly, but basers are not for everyone. I like to buy basers or close to base and then add my own rims/wheels and tires in a plus one size from tirerack etc, have the windows tinted by a shop, and add my own sound system upgrade.
