The best test for mattress comfort is lying on it in the store for five to 10 minutes in the most commonly chosen sleep position. This gives the body a chance to react to the hardness or softness of the mattress without the distraction of fluffy top layers or appealing fabric coverings.
Ask the salesperson for a side view or cutout of the mattress. Inspect the interior springs for consistency and sturdiness. Poorly constructed mattresses tend to sag and develop uncomfortable bulges over time.
Pick a retailer that offers a guarantee for an exchange if the mattress is deemed unsatisfactory after purchase. Stores that offer free delivery and disposal of old mattresses and box springs make the process smoother.