I check the Maintenance >> Background Tasks and look for errors. I have my own viz to show me the last time a workbook was viewed because if it's been over 15 months without being seen then most likely it's no longer needed. We're just starting out with Tableau so I'm looking to external guidelines as well.
We are justing starting out with server and are also looking for ways to automate and monitor some of the admin tasks.
Some of the items that we'll be planning to do.
1. Performing a weekly backup of the Tableau environment.
2. Checking to see when the last time a user logged intop the system. If not in 45 days we'll unlicense them. We have a name user license model.
3. Daily syncing of our AD groups with new users to the system.
4. Also flagging workbooks that need to be removed.