1. Pick up material belonging.Huzzah for the power of reductionism. That all looks easy, right?
2. Ask yourself - "Would I pay Money for this in a shop?"
3. If Yes, put it in the "Store" pile.
4. If No, ask yourself - "Would someone else pay money for it in a shop?"
5. If Yes, put in the "Sell" Pile.
6. If No, put in the "Chuck" Pile.
7. Repeat for every single thing that you own.
8. Sell the "Sell" Pile. Anything that doesn't sell goes in the chuck pile
9. Take the "Chuck" Pile to the garbage dump via a local charity.
10. Store the "Store" pile.
Now to get started...
Bonus Link: This endless photo mosaic that someone found on digg is really incredibly clever.