• Using a browser, connect to the top level sites of all instances of SharePoint within your environment, to ensure they are reachable.
• Log on to all applicable SharePoint servers (Web Front End, Application, Database) to ensure they are running properly. This includes any Development or Staging environments as well. Although checking the overall server health and functionality might seem redundant or elementary, this procedure is critical to keeping the system environment and users working productively.
• Check the IIS functionality on the Web Servers, ensuring that the Web Apps and the Web sites are started. This can be accessed under the Start/Program Files/Administrative Tools/Internet Information Service(IIS) Manager, then highlighting the respective folders for Web Application Pools and Internet Sites. This will bring up a listing of the sites and Web Application Pools on the right side of the MMC console, showing their status as Running, Stopped or Disabled. Restart as necessary. 
•  If any problems have been reported or have been noticed, check the event logs for the various servers and research the error codes via Microsoft’s Web Site. If there is monitoring Software in place in the environment (such as MOM – Microsoft Operations Manager), set up alerts based on the problem generating alert ID’s so that you can proactively monitor your SharePoint environment.

Weekly:

• • Monitor SharePoint Disk space usage through the built in SharePoint reports for each site collection. Depending on space usage and the speed at which the numbers change, use this activity as a chance to clean up duplicate or old data, working with the Site Owner or the individual document owner to free up additional space.
• Hold a Site Owner meeting either weekly or bi-weekly just to make sure all owners are aware of changes to the environment forecasted, or to get their feedback on how to make the SharePoint environment more user friendly.
• Check the backup jobs (can be done daily as well depending on criticality of your environment), make sure the backup files themselves are consistent in size and check the jobs for proper completion.
• Check for Microsoft Patches/Knowledge Base articles for SharePoint/MOSS (RSS Feed for MOSS KB Articles – http://support.microsoft.com/common/rss.aspx?rssid=11373&ln=en-us&msid=d65614f79e70034a979b7832fc125f25)
• Archive Event logs, if necessary.

Monthly/Quarterly:

• Monthly - Check for Operating System and SQL Patches. Work with your hardware/virtualization group to ensure that BIOS and Service Packs are applied properly to the Hardware that is running your environment.
• Monthly – Validate backups. Restore a backup to a test environment to ensure that everything is getting backed up.
• Monthly – Update Documentation. Check the validity and accuracy of any documentation that is used by the end users, site owners and Administrators.
• Quarterly- Check long term storage needs based on weekly numbers.

With thanks to collaborationnation,

Happy configuring,
Gokan Ozcifci, SharePoint Community Expert