Just remember when negotiating you have to get the upper hand somehow. EVERYTHING can be negotiated it depends on a few things.
1.timing is a huge factor
2.you must be educated on the matter you cant negotiate without it
3.you have to know what YOUR willing to pay and you have to be willing to through out that "walk away" card and go somewhere else if the dealer dosent meet your needs.
4.Negotiate in good faith. If the dealer meets your needs and gives you the deal you ask for you have to be able to do it, your past the window shopping stage.
I have negotiated some fairly large deals and havent ever felt like I got a bad deal because I stick to the rules and follow these simple steps.
hope this helps, good luck