Expressions like "sleeping together," or "going to bed" imply sex. But let's talk about what you are actually sleeping on—your mattress. It's one of the most important purchases you'll make together. After all, you spend a third of your life in bed and the quality of your sleep can profoundly affect your everyday mood and long-term health. However, for many just-hitched couples (heck, for most couples), mattress shopping can be a mystery. It's not an easy item to comparison-shop and who has tons of experience buying mattresses anyways? The good news is, this is one item on your shopping list you can take lying down!

Here are seven tips to help you feather your new nest together:

1. Size matters. When sharing a bed, consider a queen or king size mattress. We typically move 40-60 times a night and make lots of full-body turns. Freedom of motion is critical to sound sleep.

2. Shop and flop. If you're shopping traditional retail or department stores, go together, wear comfortable clothes and shoes you can easily slip off and don't be shy. Lie down for a solid 5-10 minutes and compare notes.

3. What’s inside? A new resource for the health-conscious is CertiPUR-US, a not-for-profit certification program for the polyurethane foam used in bedding (and upholstered furniture). Certified foam is made without PBDEs, TDCPP or TCEP (“Tris”) flame retardants, ozone depleters, formaldehyde, lead, mercury or other heavy metals, and phthalates regulated by the Consumer Product Safety Commission. The foam is also tested to be low VOC (Volatile Organic Compounds) for indoor air quality.

4. Buying online? It's increasingly popular, but do your research. Buying a mattress from an e-tailer is convenient, but carefully check return and shipping policies. Test their customer service response before you buy to be sure they'll be responsive should there be a problem.

5. Get a room. If you're not in a hurry, book a romantic getaway at a hotel that carries the brand of mattress you are interested in. Have you liked a bed at a particular hotel? Ask them what brand it is. You’d be surprised… concierges are often asked this question.

6. How does it feel? Whether a mattress is too cushy or too firm is highly individual. A memory foam mattress sleeps differently than an innerspring mattress. Compare a variety of types of beds to narrow your choices. Can't agree? Some couples opt for beds divided into two compartments with individual controls so each half can have a different setting.

7. Shop for value, not price. Newlyweds spend much of their time in the bedroom, and, let's face it—many marital issues are either created or solved in bed. Being tired or suffering from back pain isn't conducive to lovemaking. Buy the best mattress you can afford and consider it an investment in your marriage.

Being in the haven of a bed with your beloved is one of life's most wonderful experiences. Whether you're spooning, face-to-face, or have each other's back, your nights together can greatly enhance your relationship and individual sense of well-being; and there's no better foundation for your future days of marital bliss than a good night's sleep.

Michele Ostrove is a Santa Fe-based freelancer who frequently writes on health, travel and lifestyle topics.  She has launched two magazines: AAA Traveler, a travel publication for AAA of Northern California, and Wine Adventure, a magazine covering wine, food, travel and lifestyle targeted to women, which was distributed on national newsstands.