Don't try to immediately reduce a lot, if you want to own less, go through perhaps one drawer, take out everything, think about what you want to keep and what not. Once you've considered every object, just start over. You'll probably notice even more things you don't actually want or need that you did not consider giving away before. (I at first wanted to write "get rid of", but I don't want to imply throwing things away. I give most things away that might still be useful to someone else. Eiher to friends, family or at the hackerspace. Some smaller objects often don't get new owners. Often people don't want a lanyard, pen, pin, old magazines — especially if I don't know anyone that can read the language or is into that very obscure topic — or other objects. But at least I try to not throw it all away. It's better to give something away for free, than throw it in trash. We've got a planet to save.)

Oops, that turned out longer than I thought.