Foam mattresses offer a level of support that a traditional mattress can't. The special foam conforms to your body while you are on the mattress, but then springs back into shape when you get up. Like other mattresses, memory foam needs adequate support for the best results.
Remove your old mattress from your box spring or mattress foundation, and test it for firmness. Press on the box spring in several places and look for dips or any places that "give" too much. The Healthy Foundations website notes that "as long as it still has a firm resilient feel" you can use it witha foam mattress.
Unpack the memory foam mattress and place it flat on the ground. Allow it the mattress to decompress and to get up to room temperature. This may take up to 24 hours during the winter months.
Place the foam mattress directly on top of the foundation with the "tacky" side down.
Make the bed as normal, with the fitted sheet directly on top of the foam mattress. Mattress toppers or pads may shift when placed on the foam mattress. (SEE REF 3)