Create a budget for your purchase. At Sears, you can find mattress starting at about $550 and priced up to $1,675 or more. Decide how much you can afford to spend, and stick to that price.
Pay attention to the firmness of the mattress. Sears offers mattresses of all firmness levels, including extra-firm and pillowtop. If you're buying a mattress for yourself, Sears recommends trying it out in the store. Customers are allowed to lie down on the mattresses they're comparing. Sears recommends choosing a medium firmness level for a guest room mattress.
Check out the customer ratings for the mattresses you're comparing on the Sears.com "Mattress" page. Mattresses are rated by written reviews and by numbers of stars, with five stars being the highest.
Consumer Reports also rates mattresses and offers shopping advice.