Next time you organize your closet (I try to do this at the beginning of each new season) hang items with the hook facing towards you. When you return worn or clean clothes to your closet, hang them the normal way with the hangers facing the wall. At the end of the season or next time you clean your closet you will know exactly what you wore and didn't wear and will have an easier time knowing what to donate.
Also, try not to hang sweaters. It's best to fold them to avoid stretching.