This article is from the Macintosh for sale FAQ, by Elliotte Rusty Harold firstname.lastname@example.org with numerous contributions by others.
This final tip ought to be obvious, but many people have a hard
time grasping it. If your salesperson likes you, he or she will
be much more amenable to giving you a good price. At the larger
dealers that will give you the best prices (if you know how to ask)
salespeople often don't care about low-end sales enough to do much
hard bargaining, and will often decide how low they're willing to
go based solely on how much they like a customer and what sort of
mood they're in. (Of course if your salesperson just broke up with
his boyfriend last night you're out of luck.) Not all stores will
be able to offer you a rock bottom price. Please don't get angry
about it if they can't. If your salesperson tells you that the
price you're asking for is ridiculous, get their lowest price,
thank them, and go somewhere else.