A good centralised guideline is:
-Have only 2, maybe 3 SA-s, that way good admins will see a point, in administrating your server
-Don't keep someone, who doesn't do anything to administrate the server admin, just because he doesn't do any harm, doesn't mean he doesn't deteoriate your admin quality.
-Get a moderator system, as a stepping stone
-Don't give significant status to contributors, make a reward system
-Don't give SA, just to let someone use eval as a coder, there is a eval add-on, that let's the host grant it and revoke it from any player with a command.