I would recommend looking over /var/log/messages and /var/log/secure at least twice a day. I usually just keep both files open on the top of my screen with a tail -f on them. That way, you can tell if there are errors authenticating, the disk is full, or someone is trying to login as root from somewhere.
Regards,
--
Konstantin ("Icon") Riabitsev
Duke University Physics Sysadmin
www.phy.duke.edu/~icon/pubkey.asc