I started getting rid of my stuff few years ago by selling or donating books to my local library, selling, donating or recycling clothes... Also getting rid of some "sentimental" items such as concert/festival tickets, a bunch of photos and similar stuff I used to collect. I still go through my things couple of times a year and I find that each time I am less attached to them (and material things in general).

I think you did did an amazing job dealing with your belongings and coming up with a strategy/categories. :)