Along similar lines, I recommend David Allen’s Getting Things Done method (GTD): http://macin.files.wordpress.com/2008/11/gtdclouds_2048.jpg
I also use a couple of sweet plugins for Outlook: Clear Context Pro is amazing for folder creation and filing, and does email threading (think gmail) and color coding. It also costs a little more than I want to pay, so now I am using
Xobni, which is like a google search for your inbox. In general I think there are 2 major ways to go with organizing – foldering and searching. Diligent folder users will know where things are and keep matching files in hard copy and electronically, in outlook and their drive. Searchers will agglomerate things but use naming conventions, tags, or their own demented logic/meta data to find things. I do both, even though it doesn’t totally make sense, which is the point – it works for me.