The final version of iOS 12 isn't arriving until the fall, but a public beta is now here to try if you're curious. You don't need to install public betas on your phone, and we'd advise you not to (use a second device if you're curious), but here's what's new to try. Yes, Memoji! And there's more.
Siri Shortcuts will eventually work with third-party apps and a future new app called Shortcuts that will program all sorts of voice-enabled workflows... like the Apple-acquired app Workflow. But that's not here yet.