We name the user's home folder the same as their logon name. Then when a user leaves we place there entire home folder in an OBSOLETE folder with the date it was moved. That way it can easily be reviewed for deletion.

Example:

OBSOLETE
JMSMITH_10-15-2004
BLWARNE_09-12-2004

Then if you need disk space or if your ready to remove you can easily see by the date which ones need attention first.

There are ways or methods to automate this, but our management has opted not to automate. They prefer to review all data before deletion regardless.