Decide how you’re going to detect problems. Every now and then, an update breaks something. For example, SQL Server 2019 CU7 broke snapshots, SQL Server 2019 CU2 broke Agent, and so many more, but my personal favorite was when SQL Server 2014 SP1 CU6 broke NOLOCK. Sure, sometimes the update installer will just outright fail – but sometimes the installer succeeds, but your SQL Server installation is broken anyway, and it may take hours or days to detect the problem. You need to monitor for new and unusual failures or performance problems.
Click through to see the high-level strategy elements.