Step 1 is to make sure you aren't letting anything into your system that doesn't belong there. I find that making sure I send any and all bookmarks, articles, links, notes, and whatever through my inbox first helps a lot. That gives me another chance to look at it while Processing my inbox, before it really gets into my system. A lot of things don't make the cut at that point - it looked interesting at the point of contact, but taking a few seconds to ask what purpose it has or goal it supports gets rid of a lot.
Step 2 is to set up regular maintenance processes that weed your system. I have annual repeating projects to review my paper files, my electronic files (My Documents/My File Cabinet[*]) and my cloud files (Evernote, Google Docs). Taking a few hours every year to scan through all of those and throw things out removes a lot of the clutter. It also reminds me of things I had intended to do that fell by the wayside, and gives me the opportunity to recommit to doing them, or make a decision about giving it up.
When doing those annual purge projects, among the things I ask myself when deciding whether to keep something or not:
- is this for an active project?
- if this is for a completed project, do i really need to keep it?
- how hard would it be to replicate this or get the data from somewhere else?
- how does this support one of my current goals?
- is there any action needed for this thing?
- if I don't need it now, should I archive or delete?
Doing this kind of project annually is plenty for me. Sometimes it slides to 18 months or so. You may feel a need to do it more often, which should make the projects quicker to complete.
* My Documents/My File Cabinet
Years ago when I first set up my GTD system, I created a folder called "My File Cabinet" under "My Documents". All of my project support material that is on my hard drive goes into that folder, where there is a subfolder for each project. They are named something reasonably clear to identify the project or goal the folder supports, much like paper files. A simple alpha sort is all I need to find most things very quickly. When a project is completed and I want to archive the data, I move the folder to "My File Cabinet Archive".