Last updated 2019-01-01.
This is everything I own. I have plenty of space in my place for more things, but I find that the less room my possessions take up in my mind, the more room I have for the important parts of life.
I started doing this on March 25, 2012, because cleaning all your stuff after having bedbugs sucks, moving with a bunch of junk sucks, and I'd read Life Nomadic, in which Tynan points out that having a tiny number of things rocks.
Some other amigos have also started doing their own 99 things lists and are even more minimalist than me.
The point of the 99 things isn't the number 99, it's the idea of forcing oneself to keep only good and useful things. I (and almost everyone else I know) have a tendency to accumulate stuff, usually with the idea that it might come in handy later or is slightly handy now. This tendency ignores the costs of having so much extra stuff: it takes up physical space, it takes up mental space, it takes up emotional space, and it dilutes the other good stuff you own.
Example of dilution: my apartment got bed bugs from a bird in the chimney. We had to clean everything. There was so much junk! After doing many, many loads of laundry, I just gave away 80% of the clothes and was instantly better dressed than I had ever been. Same thing with my dishes, my cables, and the things in my wallet.
Every time I subsequently got rid of a thing, it was hard to do, but immediately afterward I felt great, and I haven't regretted expelling anything yet. This is a nice consequence of getting rid of many things: you realize that every single borderline ohhh-should-I-really-get-rid-of-this is actually an obvious yes-ditch-it-now.
Every time I subsequently got rid of a thing, it was hard to do, but immediately afterward I felt great, and I haven't regretted expelling anything yet. This is a nice conseI don't think you have to pick a number; you just need some system of forcing yourself to get rid of things in those borderline cases. If you do pick a number, it doesn't have to be 99; it just needs to be motivating. And you don't have to count things strictly; if you can't do it while still counting books, clothes, and skateboards, then count everything except books, clothes, and skateboards. I don't count consumables, I don't count some of Chloe's kitchen or cleaning things, and I count most things that are always bundled together as one thing (like a first aid kit or a bundle of backup sock).
If you decide to do a get-rid-of-stuff purge day, I think it will be great if you make three categories: keep, cull, and purgatory. Things in the third category--things you aren't sure about purging--get put away in your dungeon for a set period of time, like three months. If you didn't go and pull the thing out to use it during that time, then at the end of it, you cull it. I would also set the purge day to recur once a year, or do smaller, targeted purges more frequently (clothes this month, dishes next month, etc.).