In the late 80s, before I had my first computer, I created an index card catalog of my whole collection. At the time, it took up two of those little index card boxes. Back then I also had the physical collection itself quite organized, like this.
1. Male solo artists (alphabetically)
2. Female solo artists (alphabetically)
3. Groups (alphabetically)
4. Classical (not really sorted because most had multiple composers per record)
5. Odd stuff that didn't fit anywhere else (not really sorted, either)
It isn't organized very well anymore because first moving it from my dad's house and then eventually moving it from our old house to our new house pretty much wiped out the organization, and I just never have felt like fixing it. It would be a pretty big job.
I never bothered sorting by genre because I don't really think about that. For me there are really only two genres: stuff I like and stuff I don't like.