Apple has a distribution list you can sign up for that will tell you when OS updates are released. In typical Apple fashion the email notification is usually a day late. I also have emails enabled for JAMF Patch management, so JAMF Pro will email me when the patching definition for macOS updates.
Beyond those updates. Be active in Apples Beta Seed. You will be notified when the Release Candidates are out, and once the RC's are seeded out likely on Thursday, the updates are typically deployed the following Tuesday. .1 updates this method wont work as apple does not put .1's in the Beta Seed program.
https://lists.apple.com/mailman/listinfo/security-announce
