This is a pretty good book about how to get all your stuff organized. The first part of the book covers her general philosophy of organization and bulk of the book is made up of what she calls recipes for putting certain things/rooms in order.
It's written for a British audience so occasionally a little translation is needed.
My takeaway from the book is that the question you should ask yourself when trying to decide what to get rid of is this: would I pay to replace it? If not, throw it out.
Now, to try and put it into practice...