One tip I've used is to always say 'What's my final on the road price?' That way you are negotiating the final cost and there won't be any 'Oh, but that price didn't include the paperwork or tax or tags, etc etc.' Even with that, the guy tried to pull the old 'Oh but this specific car has a pinstripe and mud guards and a few other pieces of crap already installed so that will be extra.' I just said I was told X would be the on the road price if that isn't right I'm walking out. He went back to talk to a 'manager' and a few minutes later came back and agreed to go with the already quoted final price.
Check edmunds.com for their TMV price, when I was shopping I found them to be pretty dead on as to the best deal I could get. You could also pay Consumer Reports for their guide on the car you are shopping.
http://www.consumerreports.org/cro/...vice-and-prices-on-buying-a-new-car/index.htm If the price you have is already at what edmund's spits out, you're doing well IMO. Your best bet for haggling would be to go to a different dealer and see if they will give you the car for an amount somewhat less than you already have quoted.
Also, I found you couldn't get a serious quote any way other than being at the dealer in person. I did the internet quote thing and I was quoted a price over a thousand dollars higher through that then I got straight off in person - at the same dealership.
Car buying is a pain in the ass, but in some ways it's almost entertaining. Dealers try all kinds of tactics. They all do the 'What can I do to put you in that car today!' BS and some go further and try to bully you 'What are worried about if I will give you the price today? Are you scared to buy today? Are you just wasting my time?' Basically don't worry about pissing them off - you are nothing more than a sale to them, but don't be obnoxious just for the sake of doing it either.
The other great part about buying a car is when they switch gears to sell you the warranty plan. (Seinfeld pretty much nailed it in his stand up routine.) "Oh that car that is so great, well it's basically going to fall apart within the next few years so you definitely need an extended warranty."
ender I hear you on buying used, but when I priced newish used cars (1-3 years old with 5-20K miles) vs. buying a new car I found I could get the new car cheaper than the price at Carmax. And cars aren't investments, they are basically depreciating assets, but your point still holds.
If you have a trade-in and a Carmax in your area hit them first to see what they'll give you. My gf got much much more (I'm talking 4-5 times more) from Carmax than the dealer would have offered in trade. And if you don't plan to pay off the car right away I'd see what rate you can get from a bank or credit union and if the dealer can't compete with that finance it there.