If you don't already know, you can't treat SharePoint databases like any other database in regards to SQL Server. Here's a listing of articles that talk to what you can do. Before doing any maintenance, PLEASE read these articles. Index fragmentation is a big hotspot for alot of SQL DBAs.
Database maintenance for Office SharePoint Server 2007 (white paper)
How to defragment Windows SharePoint Services 3.0 databases and SharePoint Server 2007 databases
Information about the Maintenance Plan Wizard in SQL Server 2005 and about tasks that administrators can perform against SharePoint databases
You experience issues with portal alerts in SharePoint Portal Server 2003 or with search performance in SharePoint Server 2007 after you create SQL Server 2005 maintenance plans
Support for changes to the databases that are used by Office server products and by Windows SharePoint Services