Car Negotiation Tactics

Here is my play by play from July 2015, we were looking for a Mercedes GLK 250 Bluetech in Steal Gray with a light interior, ashwood with no options. Yes fairly specific but you only buy a car ever 5,10,15 or 20 years.

Step by Step:

1. Goto Autotrader.com and do a search across the country to understand inventory levels. More cars equals better pricing. 
2. Visit Truecar.com and perform a search for your car. They do a good job in sharing the % off MSRP which people have received on your car.
• Next send out for a few dealer quotes, yes you need to do this to understand the market. I received discounts from 6% to 9% off MSRP for the same car.
• Remember most cars are a commodity, a dime a dozen (don't listen to the dealers sale pitch) unless your buying a limited production car... 
3. Next make a list of 5 dealers near your home and visit their websites to view inventory. If more than one has your car you have negotiation power. Otherwise increase your dealer list to 10 or more. In my case I went to 25 which included dealers in Southern California. 
4. When you finally find the car you want visit the dealer and test drive it but don't seem too excited always mention I wish it had blind spot detection or I don't need the tech package.
5. We found the car we wanted but with $9k in additional options. This was the last diesel on their lot and it was loaded and I thought it might have been here for a while. Later we found the dealer had it for 10 months. 
6. Thru Truecar.com I saw 13% as the largest discount I could get based on a MSRP of $41k but on a $49.5k car one can do better. We were willing to pay $40k for the $49.5k car and knew we could get the car with no options in Southern California with a black interior (we didn't want) for $37k. 
7. The dealer came down to $45k, that was 8% off MSRP, I knew there was 5% more. The dealer asked for my email from Truecar regarding the 13% off MSRP.  Next day they offered $42.5k hinting there was a few hundred dollars left in the price or 13% off. I said i appreciate it but we needed a number closer to $40k.
•  Tip never seem impressed with their price and let em know you will chew on it. 
8. A few days later I called and said we will take another look on Friday. They emailed me a price of $41.5k which got my attention and shortly after sent another email offering $40.5k if we made the deal on Friday. I said consider it done!!!
9. Overall we purchased a 2015 GLK Diesel with a $49.5k sticker for $40.5k or 18% off and the dealer stated they lost $3,500. My better half felt bad for the sales guy. Their finance guy said don't worry he gets $250 and we make lot of money on other deals. The sales guy was happy to share he sold an SLS for $20k above sticker. 
10. The moral of the story is they win some and lose some but come out ahead in the long run. Always keep asking for more and don't buy too quickly...