Back in the day when I went on site to help SCCM customers all the time I kept a compiled list of tasks that should be done on a regular basis to keep their ConfigMgr hierarchy running well. I would share this with customers as appropriate and apparently it was handy because I was recently contacted by one of them who lost the list but was looking for it again. Rather than share to only that one customer I figured it would post it for all to enjoy. I will admit that I haven't updated this since 2015 so if you see anything new that is worthy of adding please use the comments below to share the knowledge and grow the community as well.
I will add that much of this can be done through proper monitoring via SCOM, OMS, or other monitoring software. If so then your key task would be to make sure that monitoring is active and working correctly..., maybe cause a purposeful failure now and then and make sure your monitoring catches it.
• Verify that predefined maintenance tasks scheduled to run daily are running successfully.
• Check Configuration Manager site database status.
• Check site server status.
• Check Configuration Manager site system inboxes for backlogs.
• Check site systems status.
• Check client status.
• Check the operating system event logs on site systems.
• Check the SQL Server error log.
• Check system performance.
• Monitor software distribution and patch deployment status
• Verify that predefined maintenance tasks are running successfully.
• Delete unnecessary files from site system inboxes.
• Produce and distribute end-user reports if required.
• Back up application, security, and system event logs and clear them.
• Check the site database size and verify that there is enough available disk space on the site database server to allow the site database to grow.
• Perform SQL Server database maintenance on the site database according to your SQL Server maintenance plan.
• Check available disk space on all site systems.
• Run disk defragmentation tools on all site systems that need it.
• Reinstall clients via push to a collection of machines which are potentially unhealthy
• Review client health reports and address any concerns.
• Check compliance with desired configuration baselines
* Check for any machiens needing aproval for communication with SCCM
Periodically (Monthly/quarterly, etc.):
• Review the security plan for any needed changes.
• Change accounts and passwords if necessary according to your security plan.
• Review the maintenance plan to verify that scheduled maintenance tasks are scheduled properly and effectively depending on configured site settings.
• Review the Configuration Manager hierarchy design for any needed changes.
• Check network performance to ensure changes have not been made that affect site operations.
• Verify Active Directory settings affecting site operations have not changed. For example, you should ensure that subnets assigned to Active Directory sites used as boundaries have not changed.
• Review the disaster recovery plan for any needed changes.
• Perform a site recovery according to the disaster recovery plan in a test lab using a backup copy of the most recent backup snapshot
• Check hardware for any errors or hardware updates available.