The free update is available [through] the Mac's app store. If you have any crucial third-party software or accessories, you might want to hold off until you verify that they will work properly with Sierra. Check with the software or accessory maker, or look for any complaints online. Be sure to back up your data before upgrading.
Once you have Sierra, here are things to look for:
Sierra brings two features already found on iPhones: the Siri virtual assistant and Apple Pay.
Siri can help with directions, web searches, reminders and even Mac-specific commands, such as putting the Mac to sleep. I find it odd, though, to talk to a computer, so I still use the keyboard and trackpad most of the time. Unlike Microsoft's Cortana assistant on Windows computers, however, Siri won't take typed requests in public settings such as coffee shops; all you can do is talk to her.
Where Siri helps is in letting me pin results to the Mac's notification center, so I can continually get baseball standings and scores after asking Siri just once. I can also drag and drop Siri results such as weather and maps into email, Word documents and other apps.
Apple's payment service, meanwhile, now works with websites that enable it, although you'll still need an iPhone or Apple Watch nearby to complete the transaction. Apple Pay saves you the trouble of re-entering credit card and shipping information.
The Photos app is getting new search and highlights options to match updates in iOS 10, released last week. As with...