1-2 weeks ago I picked up a 2012 370z. My boss showed me this website before he bought a car few weeks back (volvo) using this method.
It is ZAG's website
American Express | Car Buying Home Page
This will show you exactly what you can buy the car for and discounted and at what dealer. You can take the print out and literally go to dealer and pay that price! I went to look for 2011's but there werent too man with colors I wanted, so I walked away after getting same invoice pricing as listed and paying off my lease of $1500 for 2 months on my x5. I walked away and dealer calls me same night and says he can get me a 2012 whichever color/option I wanted , they just need about 4-5 hours the next day to go get the car. AND they would honor same pricing on that 2011.
Lastly, I told them I will finance, and what is the best rate they can do because I can get 1.99 through penfed so they need to match or beat it (pen fed is like 2.99 for 60 months!). They ended up getting me 1.99% financing through capital one for 60 months.