I divided music out into the following categories.
U - UIL
CM - Concert March
H - Holiday (Holiday)
CB- Concert Band (anything Concert music not above)
MB - Marching Band
J - Jazz

Each piece got an identification number like U-0010 or CB-0210. This way I would not have to keep reshuffling music around in files when additional pieces were purchased.

Finally, I kept the scores separately also similarly labeled in filing cabinet in my desk with a table both printed alphabetically and by code to help me find pieces quickly. This way, if I want to pull a score to study, its right there and I don't have to pull the entire folder out to find the score.