When looking for great sleeper sofa here’s what you should look into:

Look at the sofas construction; check all of the things you would check when shopping for a quality sofa – solid frame and construction, quality cushions and comfort, quality upholstery or leather and stitching, etc.

Sit on the sofa bed when folded with mattress inside.  Many sofas are available with and without sleeper options, if you are buying the sleeper version of the sofa be sure to try a model with the sleeper inside. It is likely to feel a little different (typically a slightly firmer feel) than the non-sleeper option.  You will probably use it more often as a sofa than a bed, so be sure it is comfortable to sit on. 

Pull out the sleeper in the showroom and try the mattress for comfort, inspect the mechanism and sleeper frame to ensure that it is solidly built to will handle use. Be sure the pull out mechanism operates smoothly and does not stick or squeak. Look for a thick steel bed frame that can solidly support weight and movement that is strongly attached to the sofa frame.  Check for smooth edges all around to prevent tears and snags on your mattress or bed linens.

Choose your mattress style.  Look for manufactures who offer you a choice of sleeper mattress types.  Some allow you to select between options like inner spring mattress or gel memory foam, giving you the opportunity to pick your preferred style of mattress.

Check sizing carefully to be sure that you have space for the sofa as it stands when closed, and also that the sleeper will fit in your room when fully extended taking into account the other furniture in your room.  Remember that you’ll want to minimize the how much furniture you need to move when you pull out your sleeper.