Knowing the position you most prefer to sleep in is your best tool for finding the perfect mattress. Different positions require different responses from your mattress in order to make you comfortable. For example, a back sleeper would be most comfortable on a firm mattress whereas a side sleeper needs the pressure point relief that a softer mattress offers. This gets more complicated if you change positions or if bedmate sleeps in a different position than you. If you don't know what position you like to sleep in most, try paying extra attention tonight as you go to sleep.