Has anyone out there bought a new car by first going to local dealers to determine eactly what you want then putting specs online and getting bids from local dealers?

I have been told that that is the best way to get the lowest price. How exactly, do you do it? Any particularly good clearing-house sites? Also how much does specifying paint colors a nd a few basic accessories affect this process? Are the bottom-dollar prices only for cars on the lot or are they for cars dealer can sell. What affects the additional offer of rebates or 0% financing? I haven’t bought a new can since long before the openness of the internet changed the process.