When I first started using comments to make play lists, I got a little out of control. I had something like 50 different words. With 10 gigs of songs, it was getting a little hard to keep up with. Not to mention my fingers hurt from having to type so much.
I decided to streamline it all using ASCII art. I'm a really visual person, and nothing takes more than three characters to type, which is nice. Here are a few examples:
<3 For songs about love
</3 For songs about betrayal/breakups
o-o Songs for working out
zzz Songs for my sleep playlist
=o Songs I like to sing along to
I'm not sure if this will work for anyone else, but it works perfectly for me.