The first thing to be considered when you are buying the futon mattress is the size. Make sure that you have the correct size of the futon. The sizes are the twin, full, queen and king.
The next thing for selecting a good futon mattress is the comfort. It all depends on the kind of mattress you are comfortable sitting or sleeping on. If you have retailers nearby you should visit the store and check the various comfort levels by actually sitting on this. The mattress can be soft, medium or very hard. There are no obvious advantages and disadvantages of one over the other and it really depends on the personal choice and ease.
Another thing to check out is the construction of futon mattress. The main thing to look for is the inner material in the mattress. The most common material used is cotton. Some of the other materials are latex, inner coils and even the memory foam. The memory foam mattress is definitely the best though it is costly than others.
Get the thickness right for the futon mattress. The thickness of the mattress will be a factor if you use the mattress as a bed. The 9 inch thickness of the mattress is the best. For average or less use get the 6 inch mattress
If you are buying online then make sure to compare the prices and the features for the mattresses and always buy the established brands