The right support. The most important factor to consider is the support that the mattress can provide to your body. This is the first thing you should pay attention to. A mattress should not be too soft, should not sag, and should respond to your weight by slowly going back to its original form. If a mattress simply gives under your weight, then it will not support the proper curve and alignment of your spine. If a mattress does not provide the optimum support especially for the key areas of the body like the lower back, you will most likely wake up to body pains.