In case you don’t read all the comments (note that it is possible to get all the comments in a single feed), I wanted to highlight an idea from Oasis in a recent comment of having a downsizing party.
You invite your friends to your home, the price of admission being a bottle of wine and in exchange they can bring away your clutter. Practically speaking, you could either mark it, put it in boxes, simply say yes or no when asked, or point out each item and ask if anyone wants it. Actually you don’t need the wine part, I just thought it was a clever idea. You could also organize it as a potluck.
In fact, getting really “primitive”—I may be overly generalizing here, but I understand what we think of as primitive people are very happy to give their stuff away (gift economy and all that)—a group could take turns hosting such parties. That way you would always keep your possessions trimmed and you might have an opportunity to acquire some new stuff. Also, it makes eating out a more worthwhile experience.
The only problem I see with this is if your friends are mostly downsizers themselves. I have run into that problem myself often enough: I got about 100 CDs I’m trying to get rid off. Do you want them? No, thanks, I’m trying to downsize. So best if you can invite some hoarders