First go through and sort out what is in the closet vs what actually needs to be there. Edit, edit, edit. Of what's left, sort like with like. Then decide if you need any storage containers (baskets, bins, etc). If you've got something lying around the house that will work, great! If not, it's time to go shopping (for containers, not more clothes!). Once you've done that, everything should have a place which means you'll be able to clean up the closet in just a few minutes. :)