Lay it out flat over the mattress pad, layering the quilts if you have several. Cover with a clean sheet to prevent dust and exposure to light. The second best method of storing a quilt is to roll it on a cardboard tube or plastic pipe. Be sure to cover the plastic or cardboard with layers of clean muslin or acid-free paper. Cover the quilt again with another sheet or more acid-free tissue.
Creases become permanent over time and cause stressed areas.
A couple of times a year take the quilt out, give it a good airing, and refold along different lines. Put your quilts someplace cool and dark, out of contact with bugs, pets, and children. Wherever you choose, be sure the quilt is not in direct contact with unfinished wood. This includes cedar chests and closet shelving. Wood contains acids, and acids are bad for fabric.