Gretchen Rubin of the Happiness Project (see my review of her excellent book of the same name) wrote a useful piece for Zen Habits called "Nine Quick Tips to Identify Clutter."
As I sifted through our possessions, I identified nine questions to ask myself when I was confronted with a questionable object. This list helped me decide what to keep and what to toss, recycle, or give away.
1. Does this thing work? I was surprised by how hard it was to admit that something was broken and couldn't be fixed–say, our dud toaster or my daughter's frog clock. Why was I hanging on to these things?
2. Would I replace it if it were broken or lost? If not, I must not really need it.
3. Does it seem potentially useful–but never actually gets used? Something like an oversized water-bottle, a corkscrew with an exotic mechanism, or a tiny vase. Or duplicates. How many spare glass jars did I need to keep on hand?
Nine Quick Tips to Identify Clutter
- The Happiness Project, by Gretchen Rubin
 - Happiness Project interview
 - Eleven myths of de-cluttering
 - Merlin Mann reviews It's All Too Much, a book on decluttering …
 - Visual clutter detection
 - Washington Post Journalist confronts his hoarding
 - Stuff: Oliver-Sacks-like account of pathological hoarders – Boing …
 - Advisor: Deleting emails could make you happier