Here are my current DBA rules. Yours will differ, but these hold me in good stead.
Rule 0: Verify your backups. Obviously I assume you are making backups - you _are_, right?
Rule 1: UPDATE STATISTICS. That will frequently save your hide.
Rule 2: Data/Log always on separate drives. Know what happens if your data and log are on the same drive, and it fills up? No? You don't want to.
Rule 3: Complexity is the enemy. Not quite KISS, but definitely related.
Rule 4: SQL Sentry's "Disable Until" is a godsend. Make sure to use that instead of simply disabling the job. And double-check the time it restarts, since SQL Sentry adds 1 day by default - not useful if you're trying to disable something for 2-3 hours.