This works for me. It might or might not work for you. But I look at everything (pretty much all the time) and ask myself "Have I used this in the last six months?" If I have not used it, or worn it, I must have an awesome reason for keeping it. If you have not used it, you ain't gonna miss it. Get rid of it.
But that's it, its kind of simple, well, because I am, but its the Six Month Rule. Twice a year. Within a year your life will be so different. I do my CDs and books once a year. If I have not read it, or listened to it in the last year, I give it away. I can't need it all that much. If you don't listen to it 365 days in a row, really, when is it up next on the playlist?
And its not about some sort of zen deal about not being attached to your stuff. Its about being attached to the right stuff, what you use, because its what you need. Its organization by function. And its not all that bad.
The aim, by the way, is to be able to do the almost James Bond deal of traveling the world with nothing, but somehow having everything he needs (well with drops by Q). But I believe strongly in that kind of minimalism. Its neat and clean all on its own, even when I'm not. I trust that.