Start by flipping all the hangers in your closet so the hooks point towards you (the "wrong" way).
Whenever you wear an item, hang it back up as you normally would, with the hook facing the back of the closet.
After six months, reassess your closet. Any hangers still facing the wrong way? Those are the clothes you didn’t wear, and it might be time to donate them.
Bag up the unworn clothes and donate to make room for what you actually love wearing!