Anna Wallner and Kristina Matisic RELATED LINKS About the Shopping Bags: Anna Wallner and Kristina Matisic VIDEO TIPS: The Shopping Bags give quick pointers on more than 100 items

By Anna Wallner and Kristina Matistic

There's nothing more refreshing and invigorating than a good night's sleep. And for that, comfort is key. To find the best mattress, we spent nights slumbering at a mattress store, testing the merchandise (even getting up in the middle of the night to switch beds!) Here's what we found:

• Coils are the most important part of the mattress's interior. Generally, the more coils there are, the firmer the mattress will be. The coil's gauge or thickness is also key. The lower the gauge number, the thicker the wire and the firmer the mattress.

• The box spring is important. It can significantly extend the life of a mattress.

• Ask about mattress's padding or foam. Convoluted foam (shaped like an egg carton) helps distribute weight more evenly for a more comfortable sleep.

• Ticking is the outside material or upholstery of a mattress. Most are made from polyester or a cotton/poly blend. A more expensive mattress will often have elaborate stitching and a fancy design. But remember, 99.99 percent of the time this will be covered by sheets.

• Check the ticking for loose threads. If the stitching becomes lose, it can lead to puckering and lumpiness.

• Pillow tops are plush and comfortable, but they do compress over time.

• Lying down on the merchandise in the store is a must. Spend at least 10 minutes lying in various positions. And if you have a bed pal, bring him or her with you, too.

• Some stores have a better return policy than others and allow you to return/exchange a mattress if you're not happy with it after a few weeks. Be sure to ask about this before you buy.

(Anna Wallner and Kristina Matistic host The Shopping Bags. Distributed by Scripps Howard News Service.)