Originally Posted by IS350jet

Expect to get slightly less than wholesale after negotiating. The typical advice is to negotiate your trade separate from the purchase but good luck with that one. The Salesman will have to configure your trade on the 4 square (a negotiation worksheet designed to create smoke and mirrors during negotiations). It's most dealers policy that if you don't want to negotiate with a 4 square, they won't sell you a car. They have to have the 4 square in every deal.
Read this.

http://www.edmunds.com/advice/buying...2/article.html

It's lengthy but for anyone buying a new or used car this information is invaluable. I found it very educational as well as quite shocking.