Foam Mattresses...

…are either natural or synthetic. “You don’t have to buy a Tempur-Pedic to get memory foam in your bed today,” Consumer Reports senior editor Tod Marks says. “Better beds, expensive beds, have enough to make your bed comfortable.” But if you do want to go for a fully foam mattress, your choice comes down to this: Do you prefer natural or synthetic materials?

"Natural” refers to latex rubber, which comes from the sap of rubber trees. Natural foam conforms to the body and is cooler because of the naturally occurring tiny holes in the material that keep air running through it. Rolf Sannes, brand director for Simmons Beautyrest, adds, “Latex is faster-responding and gives you a little softer feel, whereas memory foam feels a little firmer.”

Synthetic, or memory, foam mattresses are made from different qualities and densities of urethane. One particular type is called viscoelastic, which is what the Tempur-Pedic brand uses. “The biggest complaint (we get) is that people sweat on it and are hot,” says Bob Long, owner of Long’s Bedding, in New York City. But, again, choosing a mattress is all about personal preference, so go with what feels comfortable to you.

Box Springs...

…need to be replaced, too. If you’re getting a new mattress, think about investing in a new box spring as well. It’s the thing that looks like a mattress and goes under your mattress but isn’t a mattress. It’s basically a block of support for whatever goes on top of it, including your mattress and you. “Box springs wear just like mattresses do, but they don’t show the wear,” Long cautions. “So when you’re replacing a bed, it’s important to replace the whole thing.”

Why is it such a big deal? “The box spring acts as a shock absorber for the mattress,” Long says. “So if you have a great, brand-new mattress and you put it on a 10-year-old box spring, it’s not going to be supported correctly and it’s going to sag.” Putting a new mattress on top of an old box spring may also void the mattress’s warranty. Another point to keep in mind: Some manufacturers are switching over from a two-sided mattress design to a no-flip or one-sided design, and the support needs are different for each. “If you’re going from a two-sided bed to a one-sided,” says Marks, “you might need a new box spring.”

…come in three categories. Long recommends learning about all of them so you can make an informed decision about what to buy. “A better manufacturer will offer different grades of box springs with a mattress,” he says. After that, the choice is up to you. Here are the three options.

Platform foundations. Made of wooden slats, corrugated cardboard, and foam, these are the cheapest and, not surprisingly, least supportive. “I don’t like this (kind), but it’s what comes with most inexpensive beds,” says Long. “It’s like putting a mattress on the floor.”

Torsion bar foundations or grid box springs. These are constructed of metal configured geometrically, and they tend to be very stiff.

Coil box springs. In this type, all the coils are hand tied to one another so that they don’t all move at the same time. If you lie on the bed, the coils will give where the weight is, but the others will remain steady. “That’s the best kind of box spring you can buy, and it doesn’t necessarily have to be exorbitant, either,” Long says.