Let me start by saying that I understand my way of organizing may be a little extreme, but like anything else in my life, to each their own!
The key to successfully organizing your closet is to think about what the problem is, then start to think about what would help improve that issue. You'd be amazed at the ideas you come up with, just by thinking about what is causing the problem.
Example! My husband claims he doesn't have enough shirts to wear under his uniform. I kept telling him that he had plenty, but he said he can't find them in the closet if they exist.
The first idea that popped into my head was:
Organize his closet by shirt type.
If he knows that his dri-fit shirts are always in a specific location, he will never wonder where any are or have doubts of the quantity he has.
Then I think a step further... my husband's job requires him to wear navy shirts under his uniform. What if, in addition to having a section dedicated to his dri-fits, I ALSO organized them by color?
Instantly I have solved his issue of not being able to find his shirts, AND helped him get ready for work faster by hanging them by color.