CNN Money: Buying a car - Closing the deal

Don't let your guard down at this crucial moment or you might close out your savings.

The salesman may call it "doing the paperwork" or some similarly innocuous description. But the finance manager you are about to meet hopes to boost dealer profits at your expense with attractive-sounding offers of mechanical and financial add-ons. In most cases, just say, "no." But there are some exceptions.

If you already have financing approved, just say so and you can avoid the financing pitch. The one exception: If you already know that the manufacturer is sponsoring a promotional deal with really low rates.

The next pitch you are likely to hear is for an extended warranty. Whether you want to consider this depends on how long you expect to keep the car. If it is the three years or less that matches the typical warranty, reject it immediately. If, however, you are almost sure you will keep your car for five years or more, you might consider an extended warranty contract, which can cost $400 to $1,200.

If you decide to buy one, ask when the extended-warranty coverage kicks in and what it covers. (So-called "power train only" warranties, for instance, may exclude expensive electronic repairs common in today's cars.) Also be sure you know how long the manufacturer's warranty runs. Volkswagen and Hyundai extend power train coverage for 10 years and luxury models Lexus and Infiniti for six to eight years.

The latest vogue in add-ons (replacing rustproofing now that almost all new cars are rustproof to start with) is security etching. Having your vehicle identification number etched into the glass on your windows may, as claimed, make your car somewhat less likely to be stolen. But it is certainly not worth the $1,100 some dealers charge.