Do you have a designated spot for your glasses/sunglasses? While you can certainly just store them in their cases and in a drawer, for those of us though who tend not to use our belongings when they're hidden away, a good option is to keep them corralled in a tray, which allows them to be out where you can see 'em and easily accessible. This works whether you have two or three pairs (like me)...
or you have several pairs...
Another option is to hang them. A simple sturdy hanger works great.
Or you can create a DIY organizer using a frame and wire. Find out how to make your own here and here!
image credits: 1- photography by tinywater via the glitter guide; 2- via lonny blog, 3- photography by anh sunstrom via the glitter guide; 4- via apartment therapy, 5-via pretty stuff tumblr , 6-a beautiful mess, 7-gomming.com