When I was Internet Manager for a major car dealer, I saw my customers make the same mistakes over and over. One of the most common mistakes was relaxing after the selling price was negotiated. Unfortunately, this can cost consumers a lot of money.
The selling price is just one area that has to be negotiated with a car dealer. The interest rate you pay on your car loan, the trade value, accessories, and back-end products such as extended warranties and car-care products are also areas that need a customer's constant attention.
The mistake I saw my customers make was working hard to get the best selling price possible, and then relaxing and thinking negotiations were done. It was a mistake that proved costly to many people--and continues to be an issue.
One of the areas that customers need ongoing vigilance is the value of their trade. In truth, they should spend just as much time researching their trade's value as they do the selling price of the vehicle they want to purchase.
It's not that car dealers are doing anything wrong. But the Wild West nature of car sales means it's buyer beware. And you should know up front that the dealer is going to try and pay as little for your trade as possible.
It's important to be prepared by doing your research and at least knowing what a fair price for your trade is. It gives you something to shoot for in your negotiations. Go to Kelly Blue Book (kbb.com) and see what the expected value of your trade at a dealership will be. Look for the "Trade-in/Sell" value. This is the amount a dealer will probably allow for your trade. You may want to compare this figure to the "Private Party" value, or the price you can expect to get by selling it yourself. The difference between the two will provide a general idea of how much it's costing you to trade versus sell privately.
Car Loan Interest Rate
I provide more information in the following video on how going to sleep while negotiating your car deal can cost you money in other areas. Specifically, on your car loan: