One song on a CD isn't for everyone. I know a few Pro DJs that do it differently, I looked through Grant Smillie's wallet once and he had a couple on each, with 2 copies of every cd. The basic school of thought with only having one on a cd is that i can arrange them in musical key. So any cd's within the same area of my wallet, are gunna sound pretty gd together. Then I have the tempo and a one or two word description like: "EPIC", "LATIN", "DISCO", "FIDGET", "DEEP" etc.