We spend so much of our lives sleeping, it’s important to have a comfortable mattress to snooze on. There are two types of mattresses: innerspring or foam. Spring mattresses have coils inside, while foam are exactly that — foam. Neither type is better; it’s all about personal preference, which is why Consumer Reports senior editor Tod Marks believes that a mattress “is arguably the most difficult consumer product to buy.” Still, it’s not an impossible purchase. To find the right mattress for you, experts agree you should lie down on one for at least a few minutes. And no matter which type you choose, be sure to get a box spring to go with it. This underhyped underpiece will support the mattress and sustain its life. Here’s the lowdown on what you need to know before you go shopping for your next bed.

Innerspring Mattresses...

…come in two varieties: open coil, which is the most common, and pocketed coil, in which each spring is encased in fabric to prevent a lot of movement when your partner rolls over in the middle of the night. The number of coils is not the important thing here, since all but the cheapest mattresses are equipped with plenty. “What matters more than coil count is the gauge, or thickness, of the wire, which can affect the firmness level,” says Marks. “If you have a heavier gauge, that’s going to provide a stiffer suspension. A lighter gauge usually lends a more springy feel to a bed.” A dealer can usually tell you the gauge or you can look it up on manufacturer websites. And remember: The lower the gauge number, the thicker the coil.

…are filled with some combination of natural fibers (cotton felt, lamb’s wool, horsehair, mohair) or synthetics (most likely urethane foam). An innerspring mattress has many layers, all of which contribute to its cushiness. “Different types of foams and how they are placed on top of each other affect the comfort and the feel,” says Luis Barragan, president and chief operating officer for 1-800-Mattress. To find a mattress that’s most comfortable for you, Marks recommends lying down on a number of mattresses reflecting different price points in each of a few different brands. But, he warns, “find what you like and stick with it.” If a salesperson tells you a certain mattress is “comparable” to the one you’re looking for, that should set off alarm bells. “You can’t comparison-shop,” Marks says. “They’ll tell you what they believe to be ‘comparable.’ But we tried to buy comparables, and in four out of five instances there was no resemblance between the bed we wanted and the one they gave us.”