Nobody’s saying your neighborhood auto dealer isn’t on the up-and-up – but neither is he or she in business to give the inventory away. If you’re soon headed to a dealership, it’s time to arm yourself with as much information going in as possible.

Here are six essential points you should familiarize yourself with before you shop.

The leasing game.

Many leasing customers assume incorrectly that the monthly payment the salesperson quotes is a fixed figure, but it can be negotiated just as if you were buying the car. In fact, to keep the transaction simple, you should negotiate the vehicle price before mentioning that you want to lease.

Financing and your credit score.

Dealers like to arrange the financing for your vehicle because it gives them another source of profit. But the interest rate they offer may be higher than you could get elsewhere. Before visiting the dealership, make sure you know how you’ll pay for the vehicle. Ideally, check your credit score a couple months before buying the car so that you have time to correct any errors in your report.

Mixing negotiations.

Salespeople like to combine the vehicle price, trade-in, and/or financing negotiation, often asking you what you can afford to pay per month. This helps them provide a favorable figure in one area while nudging up figures in others. Avoid this trap by negotiating one thing at a time, starting with the price of the car – and do your homework before you walk onto the lot, please.

Loading up on the options.

Salespeople will sometimes try to make up for a low price on a vehicle by talking you into a lot of optional equipment. Research them beforehand so you know what options you want and which you can live without. Various websites and Consumer Reports’ New Car Price Reports give you dealer invoice price for all available options.

Extras you don’t need.

Another profit source for dealers are extras such as rustproofing, fabric protection, paint sealant, and etching your Vehicle Identification Number (VIN) on windows to deter thieves. Don’t waste your money. What could cost the dealer about $90 can cost you $1,000 or more.

Extended warranties.

At some point in the buying process, the dealership’s financing manager will try to sell you an extended warranty, which can cost hundreds of dollars. But most manufacturer warranties are sufficient, with bumper-to-bumper coverage of at least three years or 36,000 miles and powertrain coverage that’s often longer.