When I find myself wanting something, or holding something, or wanting to get rid of something, this helps.

  1. Do I love it?
  2. Do I use it?
  3. Does it work?
  4. If I were to buy the item right now how much would I pay for it?
  5. If I sold it now how much would I get for it?

(Source. Not sure where that came from, though.)