You can sew triangles onto the back of the quilt in the corners and put a dowel into them, it will stretch out the quilt on the top and bottom to help make it hang right. You could also position the triangles to put a dowel into them for the sides too. If it is a big wall hanging, you may want to add pockets inbetween the corners to help support the quilt.
You can also stretch it out on a painted wood frame, tacking it into place. If you plan ahead you could leave off the binding and stretch the quilt around to the back of the frame and staple it into place. These two ideas would work best on a quilt you would not plan on taking down and washing.