When people go car shopping, they usually focus on the vehicle they want — not the loan that will pay for it. But good financing is the bedrock of a solid car deal, and missteps could cost you thousands.

“Once you shake hands with the car salesman, you are not done,” says Oren Weintraub, president of Authority Auto in Tarzana, California. As a car-buying concierge, Weintraub identifies cars for clients and negotiates the deals. Getting the sales contract — and all the financing terms — right is so important, Weintraub insists on reviewing a faxed copy before his clients sign.

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While consumers know that low interest rates are desirable, there are other critical factors to consider.

Avoid long loan terms: The average car loan term has stretched to an all-time high of 69.3 months, an increase of 6.8 percent from five years ago, according to Edmunds.com. But long terms can put borrowers at risk of becoming upside-down on their loan — meaning they’ll owe more than the car is worth — and paying more in interest over the life of the loan.

While you can get loans up to 84 months, Edmunds recommends financing a new car for no longer than 60 months; used cars no longer than 36 months.

Shop your best rate: If you don’t know your credit score and what interest rate you qualify for, how can you know you’re getting the best deal on financing? Applying to multiple auto lenders lets you compare offers to ensure you get the most competitive rate — either from an outside lender, like a bank, credit union or online lender, or from the dealer.

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With dealership financing, those with excellent credit can assume they’ll qualify for the manufacturer’s best terms, Weintraub says. Buyers with midtier credit are at risk of having a dealer mark up their interest rate.

To prevent this, apply for financing with your bank or credit union before you go car shopping, says Michael Bradley of Selman Chevrolet in Orange, California. “Then let the dealer try to get you a better rate than you already have.”

Don’t focus only on monthly payments: It’s natural to want to have a low monthly payment. But beyond the extra interest costs you might incur with a longer term, focusing solely on monthly payments can leave you vulnerable in other ways. Some salesmen at the dealership may ask what monthly payment you want and then covertly inflate the sales price. “If you become a monthly payment buyer, you’ve lost control of the deal,” Weintraub says. You may overpay for the car, with the extra cost hidden in other areas, like extended warranties or extra insurance policies.

Instead, get preapproved financing. Then you can tell the salesman you’re a “cash buyer” and negotiate only the total car price.