We seem to have lost the old list of all the codes..for pro sports they are based on the team's city abbreviation (pit, chi, det, gb, sf, no, etc........) and #s 1 thru 4..1 for NFL, 2 for NHL, 3 for MLB and 4 for NBA.
Examples using my teams:
For cities with multiple teams, try their accepted abbreviations (i.e. nyg and nyj).
Colleges..spell out the full name followed by 1.
For schools which use an abbreviation colloquially such as LSU, BYU, UCLA, USC these abbreviations should work.