Here is what I usually do when I purchase or lease new caars:
1. Always do the deal near the last 4 or 5 days of the month - the sales people/managers need to make their quota and are most willing to deal.
2. If you are going to finance your car, figure out your budget and finance it through your bank. Now you have your total purchase money ready to go and you are going into the dealership with cash on hand. Your bank can usually give you a better rate on loan because you have done business with them than a dealership.
3. Once you have got your check from the bank, you are now a cash buyer and you can negotiate only on price. Find the car you want, the features, color, etc. and search Kelly Blue Book (kbb.com) and find the dealer invoice price, the price they paid for the car from the manufacturer. You should never pay over $500 this price. Print out this info and take it to the dealer.
4. Tell the dealer to give you a printed itemized quotation based upon the kbb.com pricing (be sure to include all your features) plus tax and license ONLY. Remind them you are going to write them a check and send them on their way to do their job. Tell them you are not going to do the deal unless they give you what you want. They will come back, bring a manager, bla bla bla...don't buy it. Get your printed quotation from them - tell they have 15 minutes. Be sure to have the sales manager sign the quote to make it legit.
5. If they come back with the itemized quotation, look it over carefully - does it have listed all the features, color? leather? sat radio? engine size? model?, is the price right? license and tax only? Did the SM sign the quote? If you like what you see - tell them it is a deal and go to the sales office.
If you have any questions, you can PM me. Since I live in LA, we have tons of dealerships and I usually do this by fax and pit the guys against each other. It is funny to see them fight over who can give you the best deal.
I don't usually buy extended warranties - I sell off my cars about every 3 or 4 years. So it is no use for me. If you keep a car for more than 3 years - get one and add that to your feature want list.