iOS 12 New Features, Tips, and Tricks

Most importantly, security, many of which may already be on by default
https://techcrunch.com/2018/09/17/five-security-settings-in-ios-12-you-should-change-right-now/

Some Not So Obvious
https://techcrunch.com/2018/09/17/11-neat-hidden-features-in-ios-12/

And Some More
https://www.fastcompany.com/90234155/here-are-ios-12s-best-new-features