Don't pay a cent over invoice, I paid $100 under about four months ago and got the first '08 that the dealer had sold.
The Patriot might be a nice car, but it's not in huge demand nor are there any other external factors that should cause it to be priced above invoice. Remember, the dealer gets at least a 3% holdback from the invoice price (usually around $500), as well as any factory-to-dealer incentives for # of units moved, etc. They'll tell you that 'invoice is what we pay'. Not so much, they're still getting a 5-10% profit on every deal at invoice.
Step 0 - Test drive a friend's or at a dealer if you haven't already. Annoying to get all the way to the purchase stage if only to find out you don't actually like the car.
Step 1 - Configure your Patriot on the Jeep website to find the MSRP
Step 2 - Determine the invoice price for your config via Edmunds or other online tool. The dealer ad fees (DAA and I forget the other) vary by area but they are apparently legit expenses; and may not show on some online estimates of invoice price.
Step 3 - Contact several area dealers for quotes via the internet to establish a 'going rate' for the given configuration. Use the Jeep website to ensure that the dealer you're asking has the right configuration in stock.
Step 4 (if you want) - Go to a dealer or two, do another test drive, and then get some 'general' quotes ("I'm not buying today, but I'm curious").
Step 5 - Decide on a preferred dealer - who was easiest to work with, is most convenient to your location, etc.
Step 6 - Take the best quote you've got, and go with quote in hand to your preferred dealer. Spell out what configuration you want (check beforehand on Jeep.com to make sure they have one). Ask to talk to a sales manager fairly quickly once you begin the negotiating process. Let him/her know that you know exactly how much your preferred package will cost, and don't stray from that path. Make it easy on everyone - "I know that I can get Patriot X for $18,000 from Big City Jeep, if you can match or beat that, I'd like to do business with you, if not, I will just go back to Big City Jeep."
Step 7 - If they match or beat it, and you feel comfortable, do the deal there. If not, go back to Big City Jeep.
Step 8 - Dealer extras usually get a hard sell even after you've agreed to a purchase price on the vehicle - this includes crap like VIN etching (you can get a kit from any auto parts store for $25 if you really care), 'undercoating' (galvanized steel on there already, no need for this, plus theres a standard rust/perforation warranty), and extended warranties (check out
www.chryslerwarranties.com first if you really want one, and don't pay any more than that price). If you're not prepared when you walk on the lot, you'll find that a $16,000 Patriot can quickly become a $22,000 Patriot... You'll usually get this hard sell from the financial guy towards the end of the deal.
Step 0A - somewhat out of order, speaking of the financial guy, KNOW YOUR CREDIT SCORE before walking in the door. If you have to pay a few $ beforehand to Experian, Transunion, etc, do it. You may save thousands on financing. Generally if your FICO score is above 720 you should be able to get a top-tier rate of 6-7%, and even with a score in the mid-600's, you qualify for decent rates in the 8-9% range.
Also, not a bad idea to pre-arrange financing through a local bank you're comfortable with, or through one of the online groups (eLoan, Capital One Auto, etc). That way, you can walk in with their blank check (say, up to $20k at 7%, or whatever), and ask if the dealer finance guy can beat that. In my case, they were able to arrange for a 5.9% loan with a small local credit union that I didn't even know existed. Works for me, and the dealer probably gets a little kickback from the credit union for arranging the loan. Again, everyone wins.