With the high prices of mattresses, sometimes it makes more sense to purchase a used one instead of shelling out big bucks for a new one. Fortunately, it's a simple task that requires household items. It's well worth the time.
Inspect the mattress to look for any noticeable stains, and use the brush attachment of the vacuum cleaner to remove any loose dirt. Vacuum both sides of the mattress.
Sprinkle the mattress with baking soda liberally, and allow it to sit for 30 minutes to an hour before vacuuming. Flip the mattress, and repeat the process.
Clean stains and dirty areas with a clean cloth dipped in warm soapy water. Make sure the mattress dries completely, and do not soak the mattress, as this will cause the water to get inside where it can potentially mold.
Set the mattress outside in the sunshine for two to three hours. Sunshine and fresh air are great for killing off mold spores and airing out the whole mattress. This isn't necessary immediately, but as weather allows it's a good idea to do this from time to time. Repeating the process every four to six months will help to keep the mattress smelling fresher.