Lately I've just been playing my iTunes library on full random and sorting some of my music. I like to organize songs into various playlists for various purposes: cooking, mixing, driving, sleeping, etc. What I've realized about DJing or doing a radio show is that you have to have supreme song selection. You really need to choose all 5 star songs. If you have a bunch of 4's in there, it just dampens the overall quality of the mix or segment. I guess what I mean is, even if you are "mixing" well, or even if a song fits the theme of a show and is interesting to listen to and talk about, if it's not a top tier song, you lose engagement.
Obviously everyone has a different opinion of what is or isn't a 5 star song, but sometimes it's obvious. And these are the songs you have to use to build a DJ mix set or a radio show. That's why I can't just produce a high quality mix at the drop of a hat -- or do a radio show every week or even every month. I don't have the constant flow of awesome, top tier, 5 star music -- whether it's new stuff or old. What I have is a great variety, and access to lots of different stuff -- I just don't always know what is, or how to pick, find, dig up, and sort through stuff to find the best, illest, tracks...
When I hear it, I know it, I just don't always hear it, or know how to put myself in the right position to hear it.