Transient, I really appreciate this thread. I have lots of tips that I work at weaving into my own decluttering project at the moment.

Creating a system for keeping what is essential. For instance, I am going thru paper files (p-files) and folders from my years as a consultant. I did some great work, and I find flipping through a binder better for inspiring current ideas than searching my computer files (c-files). Also some of my c-files are in an old format (appleworks and clarisworks) that is no longer 'supported' so getting to them is a bit of a pain. Therefore, I made some rules:
A. I keep just one copy of my best work.
B. Put this copy in a plastic sleeve and place in a binder for organizing later.
C. Everything else can go.
D. The goal is to reduce a 10-inch p-file stack to 2 inches or less in line with the 20/80 rule: 20% of something contributes 80% of the benefit.

Another tip: some things are simply outmoded. These are the easiest. I look through beloved articles clipped long ago briefly one more time and say my goodbyes.

With the internet, there are so many things that people are willing to share that you don't have to keep it around "until it may be needed." There are book sharing site like paperback swap, local tool libraries, public libraries, etc. People say they would like to come see my library. I say they don't need an appointment, it's the university library just down the road from my house.

For my own project: I have one shelf, and two long file drawers on deck. I am a bit more inspired to get to them. This is also therapy for me as I find writing or talking about my strategies sometimes makes them even stronger.