A mattress. (BIGSTOCK)

There is no better time than year’s end to evaluate certain areas or items in your home, and one of the most important is your mattress. It directly affects your ability to get a good night’s sleep, which is tied to your health and wellness. If you are in need of a new mattress (see telltale signs below), here are some important things to know before you shop.

Comfort is subjective

What is comfortable for one person might not be to another. The best way to shop for a mattress is in person. Ultimately you can order your mattress from an online source, but first do your due diligence. If you are a couple, shop together and if possible bring your pillows with you. Make sure you lie on a mattress for at least 10 minutes in your normal sleep position. A mattress should gently support your body at all points and keep your spine in the same shape as if you were standing with good posture. Be cautious of the word “firm” and never rely on labels to tell you which mattress will give you the right support.

It’s what’s on the inside that counts

Basically, there are two types of mattresses: innerspring and foam. Neither is better; it’s just about personal preference.

Innerspring mattresses, which get their support from metal coils, are the most common. Don’t let a salesperson convince you that a mattress is good based on the number of coils it has — it’s not important. What is important is the gauge, or thickness, of the wire the coils are made from, which affects the firmness of the mattress; heavier the gauge, the stiffer the mattress; the lighter the gauge, the springier the mattress. (Remember that the lower the gauge number, the more durable the wire is. For example a 12-gauge wire is thicker than a 14-gauge wire. )

Foam mattresses are filled with a combination of natural fibers and synthetics. When most people think of foam mattresses they are thinking of memory foam or viscoelastic foam that molds to the contour of your body. Expect to pay more for one of these mattresses — at least $1,000 for a queen.

It’s more than just a name

It is very difficult to buy a mattress based on name only. Manufacturers make minor modifications to their mattresses — for example, changing the exterior cover and model name — for each retailer. This means that the same mattress will be sold by different retailers under different names and most likely at different prices. The best bet is to go with what feels good to you.

Skip the bells and whistles

Mattress prices can be driven higher by unnecessary special features. Some manufacturers say that wool- or silk-covered mattresses help to keep you warm or cool — a claim that is questionable considering you are covering the mattress with a mattress pad and sheets and thereby eliminating any direct body contact. Similarly, don’t be taken in by the look of a mattress covered in beige damask or 800-thread-count sateen; you are going to put linens on it the minute it’s on your bed.

Warranties cover only defects that occur at the time of manufacturing. If a spring pops out of the mattress, that’s a defect. If a mattress starts to sag and lose its comfort after several years, that’s normal wear and tear. Don’t be swayed by the offer of a 10- or 20-year warranty; they are hard to claim. Instead make sure you buy from a store with a generous return policy, so you can return the mattress if you feel you have made a mistake.

To flip or not to flip?

Most manufacturers recommend that you flip your mattress every three months to prolong the life of the product and minimize body impressions. However the market is flooded with no-flip or pillowtop mattresses — mattresses that have an extra layer of foam or other stuffing sewn on one side so that they never can be flipped. These mattresses, which have grown in popularity, don’t necessarily have a shorter life span, but they do tend to cost more.

The other notable difference in a pillowtop mattress: You will probably need to invest in new sheets; look for sheets labeled high-profile or deep-pocket. They will fit mattresses from 12 to 18 inches thick.

Don’t buy one without the other

A box spring — or slats, in the case of a platform bed — acts like a shock absorber to prolong the life of your mattress and provide more consistent support. It will also help reduce the motion you feel when you or your partner tosses and turns. Box springs, like mattresses, wear out. If you lie directly on your box spring and it feels uneven or you roll toward the middle, then you know you need a new one. Be careful of trying to save money by buying just a mattress and doing without a box spring. The two are actually designed to work together, so if one is worn out, then the other probably is, too. In a short amount of time a new mattress will conform to the weak areas of your old box spring and reduce the amount of support and comfort you will get.

You know you need a new mattress when . . .

●You can feel the coils.

●You wake up with aches and pains.

●You sleep better in beds other than your own.

●You can see depressions in your mattress where you usually sleep.

●You have had your mattress for more than 10 years.

Mayhew, a “Today” show style expert and former magazine editor, is the author of “Flip! for Decorating.”