Congratulations !!!! You got the deal you were looking for. Now is the perfect time to mention to the dealer that you are looking to trade in that car you are currently driving. This way they cannot jack up the new car costs and offer you more for your car to make it seem like a better deal. If your trade-in is in good shape you should be looking for a price somewhere between retail and wholesale. If your car is spotless make sure the dealer knows he will not have to recondition it. Most research sites list trade-in value in the pricing reports, this is a good starting point. If your trade-in is less than perfect don't expect more than wholesale price. The dealers will take clunkers but they end up on the auction block the next week.
Once all the numbers are crunched and the papers are filled out double check everything before you sign. Also look out for extras, which you do not need. Rust proofing is rarely needed as most manufacturers already offer a rust warranty. Also window etching, extended warranties and accent packages are highly overpriced and sometimes useless.
Now would also be a good time to inspect the vehicle one last time. Check for paint blemishes, how much gas is in the car (some dealers will actually empty the tank leaving you just enough gas to get to the closest station) and that it is the exact model you test drove.
Now sign the papers and drive home in your new car. Pat yourself on the back for a job well done.
Kevin Schappell maintains http://www.carbuyersclub.com where he gives advice on car maintenance, buying, selling, insurance, and financing. A mechanical engineer and car guy, Kevin has decided to spend his online time helping others learn about automobiles.