If you've upgraded to macOS Sierra, then you know you now can have Siri do your bidding on your Mac. You can activate Siri by clicking the icon in the menu bar or the icon in the Dock, or by holding the Command key and space bar together. But you can't activate Siri by voice unless you do a bit of work first. Here is an article that explains how to set up Siri voice activation on a Mac. Is it really worth the effort when it's easy to activate Siri by just tapping on an icon? Well, that's for you to decide after reading the article. If you've upgraded to iOS 10, then Siri is ready to do your bidding on your iPhone and iPad as well. Again, a little voice activation setup is required. Just go to Settings, scroll down to Siri and turn her on. The iPhone or iPad will tell you what to do next. Starting with the iPhone 6s and above you can voice activate Siri without being plugged into power. With the iPhone 6, though, which I have, it has to be plugged into power before Siri will respond to a voice. This is no big deal as Siri quickly responds just by holding the Home Button a bit.
Although I haven't used Siri extensively, she can be quite handy. Here is an article with 67 handy Siri tips you might try. For example, if you're flying somewhere and want to know the status of your flight, just ask Siri. I like that. Look at tip #16. All these tips should keep you busy for awhile with Siri.