Buying a new car

I'm buying the new BRZ in cash by the end of this week and am test driving at three different dealers today. I've never bought a new car before. When I bought my current car second hand car (08 bmw 135i) 4 years ago, I offered 3k below driveaway, walked off and got a call from the dealer accepting my offer 1 week later. What should I expect in terms of negotiation or how should I go about negotiation? Driveaway is 44,000 without any options, and the only things I'd be after are mats and tinting.

EDIT: I got to 44900 driveaway including tint, ceramic coating, mats, boot lining, and 5 years manu warranty extended to 8 years.