I just assume not do the dog and pony offer show with them. At the very least I will save hours upon hours sitting in the dealership offering and counteroffering.
I have only bought 2 new vehicles in my life, which happen to be the only 2 purchased from a dealer. What I found was unless you personally knew the manager he was hiding in his office and you are stuck with a salesperson. The first thing they ask is what kind of car/truck, and the second thing they ask is what you want your payments to be. They do not want to talk price, they want to talk payment, which is a lot smaller number than the one on the window sticker. When they ask the question about payments tell them you are paying cash, this will avoid the long wait at an empty desk while they run your credit record and forget to hand you your ID back, holding it hostage until you give in. Oh, and never let them take your car to check it out for trade in value because they will hide that too in an effort to pressure you in to a sale.
You want to pay cash and you are not planning to trade in your car. Look around, find what you want, haggle on the price, slowly walk towards your car, tell them it is more than you expected a new car to cost, and haggle some more and if they come up with a reasonable price slow down and make small talk but keep coming back to the 'more than you expected' and ask them why it costs more....make them try to sell the car to you. The more they talk the better your chances. If you get a solid offer, preferably in writing, then start asking if they have any 0% or 1% financing....which might make it worth your while to finance and hold on to your money (which you probably don't have). Or if possible get a finance estimate from your bank or credit union, it may or may not be better but it is added info on your side. Then if you were planning to trade in old faithful you can ask, just out of curiosity what they would give you on trade.
With this method you will have to be patient and not need the new vehicle yesterday. If your plan is to drive home the new car now you may not be able to work this to success. My nephew stopped at the same 2 dealerships every day after work for 2 months. Talked to the sales people each day about the price, alternated which dealer he went to first, using their prices against each other. Finally one day the big boss came out as he was starting his truck to go home and said name your price. He got top dollar for his trade in (which was paid off) and bought the Dodge Cummons Turbo pick-up for less than invoice. The dealer made their money from the factory kickback.
Also, find an option they have on all the vehicles and ask if they have one without it, such as leather seats. When I bought my Avalanche in September, 2001 all of them on the lot had leather interior, luggage racks and running boards. I didn't want any of them so I decided to order one the way I wanted it, but they wanted to knock off the upgrade price (for what was not part of an upgrade package). This could be another way to knock off another couple hundred bucks. After getting nowhere (or actually no selection on options I wanted) with the dealerships in Southern Nevada I ended up calling a distant relative (an in-law of an in-law) who managed a dealership in Utah. I had him order the truck for me (after I learned I had a family member who could get me employee pricing and haggling was no longer an issue) because the sales people here wanted to sell off the lot, not help me order what I wanted, even though I was actually paying cash, checkbook in hand.
The next new car I bought 3 months later was a 2002 Dale Earnhardt Monte Carlo. The salespeople in Vegas had a couple to sell but I bought it in Utah. Being it was a limited edition vehicle I could not get employee pricing, but I got a good price because I was a repeat customer and they got a sale because they helped me the first time.
When I brought both vehicles in to the local dealership to show a friend in the parts department the salesperson was pissed at themselves for not working with me on ordering the Avalanche. They missed out on two sales.
Moral of the story: be very patient and make them "sell" the car to you, don't beg them for a better price.