My company has been on the IBM AS/400 (a.k.a. iSeries, System i, etc.) platform for many years. Our staff includes some RPG developers to develop our in-house applications and a system administrator to monitor the box, deal with backups, etc.
The writing on the wall is that we'll be switching over to SQL Server exclusively in the next year. We've already begun the transition; our new IP-PBX/auto-dialer uses SQL Server 2008 extensively. We are working our way up the learning curve with SQL Server, but none of us can legitimately describe ourself as a DBA.
So far, we're backing up the database. That's about it. What other maintenance tasks should we be doing on a regular basis to keep the database happy?