If it's for a competition, then I make a rod pocket per competition specs.
If it's to hang in a gallery or for display at home then I use a couple of different methods depending on the weight of the quilt. For larger/heavier quilts I make a rod pocket and slide a flat metal rod in it. Then I either use command strips or nails to affix a couple of metal plates to the wall to which I attach a magnets that are strong enough to hold the quilt. This way the hanging mechanism is completely hidden and it's easy to change out quilts.
In a pinch I have also used the magnets on the front of the quilt and skipped the rod pocket, but some heavier quilts will slide out from between the magnet and metal plate so I usually add a couple of tiny binder clips that I nail to the wall using very tiny nails. These aren't strong enough to hold most of my quilts up on their own, but they do have just enough hold to keep the quilt from sliding down when used in conjunction with the magnets. This is pretty unobtrusive.
Rob