The firmness of your mattress can affect the quality of your sleep. To know how firm your bed should be, consider your height, your weight, as well as your sleeping position. Soft mattresses are ideal for those who tend to sleep on their side. Medium, or medium soft, on the other hand, is perfect for those who often change their position in bed as the mattress will still be able to give support. If you are a back sleeper, go for a medium firm bed as it gives your spine adequate support. On the other hand, if you have a back problem or overweight, or sleep on your stomach, choose a firm mattress.