Newsforge's 10 commandments of system administration

Newsforge has a nice collection of articles for system administration titled
The Ten Commandments of System Administration

In short:

1. Thou shalt make regular and complete backups
   Use whatever floats your boat for this one - amanda, rsync, tar, etc.
2. Thou shalt establish absolute trust in thy servers
   using file integrity tools like tripwire, aide, and afick.
3. Thou shalt be the first to know when something goes down
   using tools like Nagios, Big Sister and Zabbix
4. Thou shalt keep server logs on everything
5. Thou shalt document complete and effective policies and procedures
6. Thou shalt know what cable goes where
7. Thou shalt use encryption for insecure services
8. Thou shalt not lose system logs when a server dies
9. Thou shalt know the openings into your servers
   using the well-established nmap program.
10. Thou shalt not waste time doing repetitive and mundane tasks