Folding it on the bias is one option, and takes up the least amount of room:
http://appliqueandpatches.blogspot.c...t-folding.html
Also, as I wrote elsewhere yesterday, my friend uses this method for her antique and heirloom quilts:
PVC pipe inside the pipe insulation (flimsy like pool noodles) wrapped in muslin. The quilt is rolled around this. And is placed in an holder (like a sleeping bag) made out of Tyvek. It can easily be stored on the shelves in the closet without getting creases.
I also saw a way to hang these quilt mummies but you need a lot more dedicated room.