I got the idea for DR RLP who was doing his CD collection in this way. I have major groups first:
War Movies
Musicals
Horror/SciFi
etc.
Alphabetical by title. Because I use loose leaf notebooks - the LARGE ones - and three hole punch disk sheets (4 to a side. 8 disks per sheet) I can add or subtract sheets as needed, and I always leave a few blank spots here and there for additions.
All of the Box Sets are kept in their original containers, tv seasons, special multidisks sets (Cleopatra, etc) I did it this way to save ROOM. It really did compact the size of the collection! I am not quite finished, I have a few shelves of discs to go....but I am making progress.