Updating and remodeling your home is a no-brainer. Ripping out old carpet, rebuilding a deck or installing energy-efficient appliances add immediate value. But homeowners don’t always see the return on investment of a new mattress.

According to research by the International Sleep Products Association, the typical American consumer keeps a mattress far too long — an average of 10.2 years. The vast majority of consumers are unaware of the signs of mattress deterioration and rarely connects the condition of their mattress to a decline in sleep quality.

Where do you start? Like most savvy shoppers, you’ll probably begin with a budget. “Most customers come in with a price level in mind,” says Scott Fontaine, owner of three Mattress Gallery stores located in West Lebanon, Claremont, and Tilton, NH. “But what they need is a comfort level.”

Take Off Your Shoes

There are around 40 brands of mattresses. According to Consumer Reports, Sealy, Serta and Simmons account for nearly three out of every four mattresses sold. Innerspring mattresses — coiled steel springs sandwiched between layers of padding — are the most widely purchased type. Although you could shop by name brand only, the best way to choose a mattress is to test a variety of beds.

Side sleepers should look for a softer mattress — supportive but with enough give to conform to the bumps and curves of the body.

Be prepared to lie on the bed as you would at home. (Many retail stores have a plastic sheet on the bottom third of the mattress, so you don’t even have to take your shoes off anymore.) You may feel self-conscious, but try out a variety of positions: side, back, curled into a ball. Stretch, toss, turn.

One sign that you’ve got the right mattress is that your body is able to relax, with your spine supported in its natural curve. “If the customer is lying on their side, we go right behind them and look at the hip, back and shoulder,” says Shawn Marsh from the Mattress Giant in West Lebanon. “They should all be the same height. If the shoulder is too high, they might need a softer mattress to take in some of that shoulder. If the hip is too high, a firmer bed might be in order.”

According to Abed.com, back sleepers should look for a firmer mattress. A mattress that gives too much or bends inwardly will not be supportive enough for the spine. Side sleepers should look for a softer mattress — supportive but with enough give to conform to the bumps and curves of the body. Sleeping on your stomach is irritating to the neck and back but, if you must, pick a mattress that is soft enough on the surface to substitute for the lack of a pillow.

Coils and Padding

What’s in a mattress? There are a few components to consider. Coils, for example, are the springs that support you. A basic mattress has 300 coils; bigger units run 500 to 700 coils. More coils will provide better support for your back. This is not to say that a 300-coil bed is a bad bed; you may like that level of support or it may be perfect for a guest room used a few weekends a year. But if you are looking for a firm mattress, go with more coils.

Coils also have different thicknesses; heavy gauge coils will provide more support. According to whatsthebest.net, a Web site that helps people make better buying decisions, don’t get low coil count with heavy gauge — the mattress will become lumpy quickly because it does not have enough coils.

Fontaine, who has been in the mattress business for more than eight years, says that you can find a proper support system at any coil count. “You can compare coil counts within a company to get an idea of comfort level, but comparing coil counts from company to company doesn’t make sense,” he says. “Each company has a different mattress-building philosophy. Within a brand name, however, coils mean everything.”

A mattress also has middle padding (foam starting below the quilted layer) and insulation padding (lying directly on the springs). The mattress’s outermost layers — the ticking or upholstery — provide surface comfort. Furnituresmart.com notes that toppings on today’s beds range anywhere from man-made polyfoams and fibers to latex and even natural fibers such as wool or silk in some of the better beds. Although natural fibers tend to hold their resiliency longer than traditional stuffings, they do cost more.

Keep in mind that the upholstery always breaks down first. “The steel springs aren’t going to break down, but the padding in between them will,” says Fontaine. A good test, he says, is to punch your old mattress and see how much dust flies. “That dust is the foam inside breaking down.”

Buy Big

“Research into sleep habits shows that a healthy sleeper turns between 40 and 60 times a night, including around a dozen full-body turns,” says Arthur Grehan, executive director of the American Innerspring Manufacturers (AIM), a non-profit trade group that provides free information on restful sleep and sleep surfaces.

That’s a lot of motion for one person in a standard 38-inch-wide twin bed, Grehan says, and it’s often even more noticeable for two people in a standard 53-inch-wide double bed. AIM says that one adult in a bed should shoot for at least 40 inches of width, and two people sharing a bed should try to get at least 30 inches each.

The queen-sized innerspring mattress is fast replacing the double bed as the standard for two people. According to the International Sleep Products Association, queen (60-by-80) and king (76-by-80) mattresses together top 42 percent of overall shipments of mattresses.

Get a Set

The mattress and the foundation, a hard platform that rests beneath the mattress, are designed to work together. The Better Sleep Council describes a foundation as a “giant shock absorber, taking the normal wear and tear of nightly use.” It lends added support and durability, absorbing half of the total weight of the sleep set.

“Each company has a different mattress-building philosophy. Within a brand name, however, coils mean everything.”

Whether you prefer a box spring (a coil unit that provides more resiliency) or European-style wooden slats, it is a good idea to replace your foundation whenever you replace your mattress. Putting a new mattress on an old box spring could void your warranty. In fact, by using an old box spring the mattress will last one-third as long as one on a new box spring, according to whatsthebest.net.

What to Expect from Retailers

All retailers have different services, but there are some standard questions you should ask. Is delivery free? Do you remove the old mattress and box spring? Is set up of the new mattress free? Can I sleep on the mattress for 30 days to determine if it is the right mattress for me? (This is called a comfort guarantee.) What’s the warranty?

A good mattress retailer shouldn’t put any pressure on you. A “comfort test” is what’s important. “We’ll start you at two or three beds at the top of the line,” says Fontaine. “Then you should go up and down the line to find the right feel. Wherever you land is where you feel comfortable.”

Fontaine suggests spending at least 45 minutes testing mattresses. “It’s expected that people may take up to two hours,” he says. “If you’re going to have a bed for 10 to 15 years, spending a couple hours testing mattresses is not a bad idea.”