Longer-lasting sofas generally have springs, and there are many types. The highest level of support is offered by a pocket coil spring, similar to those in a mattress, or a serpentine-style spring.

There are other methods of support, such as webbing. Although this is a cheaper method of suspension, webbing can offer good support if used in conjunction with springs in the areas that will bear the most weight: the seats.

That might sound like a silly question, but the truth is, nobody likes sitting on the crack. So if you get a sofa with two cushions, expect just two people to use it.

To accommodate more people, get a sofa with three cushions or a single long cushion, called a bench cushion. Sofas generally come with one of two types of backs: a pillow back, which has removable cushions or pillows along the rear; or a tight back, in which the upholstery is tailored to the contours of the sofa's back.

Pillow-back sofas are generally considered more comfortable and inviting, but there's a downside: Unless you're diligent with your fluffing, the cushions will usually look slightly askew. If you're the kind of person who is driven to distraction by something like that, you might want to consider a tight back.