Figuring out keywords for contextual retrieval is one of those things that is simple to get started on, and hard to finish well. To start, identify situations when you commonly listen to music. Your typical day, your typical week. Write those down. Next, think about your occasional situations, like having friends over or whatever else you do. Write those down also.
Now factor those contexts into as few keywords as possible so you don't have too many tags to fill out for each track, but you can still pull appropriate music for your listening situations.
When factoring, consider what varies based on general criteria like energy level or approachability. I've found that for music I've tagged as "social", the difference between a quiet dinner and a larger party later is mostly energy level, with a little more edgy stuff later (I use digger to contextually pull music from my library for listening).
The rest of this doc is notes about various keywords. Hopefully you'll find it helpful.