I think that for me the biggest thing was knowing my own strengths and weaknesses. I am not easily talked into things, but I do start to trust when I shouldn't. So I had to go into this with a clear idea of what I did and did not want and readiness not to waver on that.
I did a lot of research first. In reality I did a lot of research on the wrong car because I was convinced I wanted an Equinox until about 5 days before I tried out the Forrester. I also gathered information on comparable cars because I knew I wasn't supposed to let the dealer know I really wanted their car. That let me counter things with "well, I'm pretty sure the Equinox also is rated for higher mileage. Not by much, but some", which shows I'm not doing this blind. Had I been actually testing the Equinox I probably would have made sure I was full of facts about the Honda CRV and Toyota Rav4.
I find Consumer Reports really helpful with major purchases and this was not different. I read their instructions on test driving before I went and was therefore ready for some trickery. I didn't get much of that from this dealership, in fact I only caught her once and that may truly have been nothing more than her not thinking (the 2011 model has a different engine with more expensive oil but fewer changes. She was recommending a 2010 which probably was just to get rid of 2010s). If I did catch a discrepancy with any dealer I called them on it.
After I had driven the Forrester and knew it was what I wanted I started doing a lot of research on it. I used edmunds.com for this. Edmunds has this thing that lets you find out what you should be expecting to pay for the car you want in your area. It also has tons and tons of reviews, consumer reviews, etc. There is a piece on there I was fascinated by; they sent a journalist out to sell cars at 2 types of lots over a few months and write about it. What he shares is fascinating, including that the first job he got he was hired (on the advice of another car salesperson) based on his answer to "what makes you want to see cars". The answer: "I want to make a lot of money". There was a lot of information in that story.
I also was able to submit requests for pricing to several dealers through Edmunds. Subarus aren't common around here so there weren't a ton of choices. But I found this very educational. When I test drove my car I felt comfortable with the young woman selling the car and she proved herself by answering every one of my thousand questions over the next several weeks. The other dealerships ruled themselves out during the brief period of negotiations. One dealership actually got angry when I asked to test drive a 2010 loaner they had when I said that unless it had what I wanted and was a good price I wasn't really ready to buy yet. Their snottiness got them sent to spam right away. Another refused to deal at all on the internet. One thing I know about myself and that was really shown to be true for most people in my research is that if they can get you into their bargaining area, on their turf, they'll get the best deal for them. So they were excluded. The 3rd dealership kept giving me great prices, but not on the car I was reqesting a price on. So I'd go back to my salesperson and say OK, here's the offer from ________ and she'd say "um, check on that. It doesn't make sense and this is why (inevitably it would be that the dealership would lose thousands of dollars)". Each time they were quoting me the wrong year, the wrong model, whatever, again to get me to come in and then find out "oh, that's a mistake if you want a 2011, THIS is the price for that". They also kept offering to knock money off and give me coupons and things if I'd just talk to their finance person.
The place I dealt with wanted me to give what I thought was a fair price. This was hard as I have this guilt that they may not profit enough, which is goofy since they're not taking a deal where they don't profit. The biggest trick with my car was that I wanted remote start which had to be purchased and installed as an add-on, and that was expensive. But finally I told them if I could have everything I wanted under a specific price I'd take it. Suddenly that remote start got a lot cheaper (like free I think). I knew from Edmunds that this was a totally fair price, a few hundred less than average for this area.
The other thing that I did that I'm really happy about is that I got precisely what I want. I think I mentioned that I had 2 things I really wanted and beyond there are a lot of "luxuries" on this care because it's not the base model because one feature I wanted required the 2nd level up. That feature is adjustable lumbar support and well, let's just say 4 hours in the car daily, sometimes more. The other thing I really wanted was remote start. This saves me going on the ice to start the car to warm it, which isn't great for my ankle. That they had to put on the car, but like I said I managed to get it for a good price. The other few things I wanted were things I found out about after I trialed the car, little things like a cargo net, a screen to cover the back area for privacy, and this thing that goes over the back part that is hoseable to keep it clean. I like that idea a lot. So those few things were only a couple hundred dollars.
Normally the dealership is going to try to say "we don't have just those features, but look at this car" and they may even take some off the car with the other features but it will still cost more and still you'll have things you didn't want to pay for. That was one of the things the bait-and-switch dealer kept trying. I'd ask for a quote on "exactly this car: 2011 Forester premium with remote start, cargo net, cargo cover, and cargo tray and nothing else" and I'd get a quote for (if he was really with it) a 2011 with remote start, package A (which includes my options plus other things for about $300) and one other additional feature I didn't want, like integrated GPS. I have a brand new GPS unit, why do I want another? So I got them (and they offered because the person who wound up making the sale did listen) to trade for a base model with no features and put on what I wanted. I also could have ordered a car even more specific to what I wanted but then I'd have had to wait 2 months and for various reasons I want this done by 12/01/2010.
The biggest struggle I had was making sure I was getting the best deal and not going with the person I liked. I became pretty sure though the 3rd time the other place quoted me for a car I did not want.
Now I'm in the phase of avoiding extras. I had an extended warranty on my last car and never used it be did like the piece of mind. However, I'll blow through a 100,000 miles in a year or 2, so it doesn't make sense now. I also just turned down scotchguarding and waxing (read what Edmunds has to say about those extras, it may be in the journalist turned car salesman thing), and a maintenance plan. The maintenance plan may make sense for someone who was not going to use up the miles included in the next 6 months, but I am, and it also is difficult as I live an hour from the dealership (any Subaru dealership), so I won't even get there easily. The only extra I'm interested in is there is a car/homeowners discount policy for Subaru owners and I will check into that.
Otherwise, I'm trying a new tack to get through the signing part fast. I was very honest about my whooping cough and that I would not be contagious but probably would wear a mask (it's very hard to cover your mouth through the whole cough when it hits) and that I needed kept away from infants, etc. My bet is they get me out of that dealership FAST.
This may be be the best method, but for me internet dealing levels the playing field by removing shyness.
I'll still be very glad to be done with this.