I've given up on traditional car dealers. I just go to CarMax. They have very competitive fixed prices on new and late-model used cars. Here is a write up on my experiences with them:
The CarMax Buying Experience: No Fuss, No Muss, No Negotiating, Few Hassles
Otherwise, I'd look into buying programs from credit unions, CostCo, AutoBytel, and other organizations.
Finally, if I was buying from a dealer, I would make sure that my wife was completely in on the car selection, but that the negotiation was in my hands. She'd be left at home. No need for anyone to tell the sales dude that they are "in love" with the car. Then, I'd search the internet, know my prices, shop multiple dealers, and be completely ready to walk out. Take a stubborn jackass with you who thinks you are an idiot to buy a new car.
I'd be careful to say no to any extra stuff like dealer warrantees, stereo upgrades, GPS units, undercoating, and anything else that sounds like dealer jack. The one time I bought a new car, I asked for a stereo upgrade and I'm pretty sure they gave me the middle of the road stereo and charged me the premium stereo price. The mistake cost me about $400 on a $10,000 car.