Even shoppers who don't have smart phones can use online resources to help them navigate the car-buying process. Online calculators, such as Bankrate's auto loan calculator, can help shoppers determine the size car they can afford, especially if the buyers plan to finance their purchases, says Morris.

He suggests never negotiating a car loan without first tallying the numbers. "You can use the online calculator to input the interest rate and term of the loan. Hit 'submit' and it can show you how much you can afford to borrow," he says.

Morris advises consumers to try different scenarios when using the tools. "Calculate how much you'd pay to buy a car versus paying cash, or leasing the car," he says.

Without knowing the hard numbers, a car buyer can become emotional when purchasing a new car, and they may not negotiate from a strong position, says Morris. When that happens, the buyer may agree to pay thousands more for a car than he can really afford, he says.