1/ Use Recent iItems — Under the Apple Menu at the upper-left of your screen is an option labeled Recent Items. Hovering over Recent Items (above) will show you the files and applications you worked with recently, and within a couple of seconds, you can open one. (And here’s another quick tip: hold down the Command key – there’s one either end of your Spacebar – while you’ve got that menu up to reveal where those items are in the Finder rather than opening them.
2/ ‘Spotlight’ your files — If you either click on the magnifying glass at the upper-right corner of your screen or use the associated keyboard shortcut instead (it’s Command-Spacebar), you invoke the Spotlight search window. Type in the name of the file you’re looking for or a keyword that appears within it, and you can open that file by just pressing Return if it’s the top result.
3/ Files from the Dock — Under modern versions of macOS, you can right- or Control-click (hold down the Control key on your keyboard and then click) on some programs’ Dock icons to see recent items that have been opened with that app.
Click on one to open it, and it opens.
4/ Ask for your files, literally — Sierra’s version of Apple’s voice assistant Siri lets you search for files using your voice. Just click on its colorful menu bar icon to get started.
Try “find files I opened yesterday,” or “show me Pages documents on my Desktop”. Siri is really handy for quick searches, assuming you’re not embarrassed to be talking to your Mac. When you find what you’re looking for, double-click it within Siri’s window and it opens.
5/ From within apps — Open almost any app (Nisus, Pages, Word, Numbers, Indesign, Photoshop, GarageBand …) and choose Open Recent form the File menu. This is handy if you’ve chosen Clear Menu from the Recent Items menu in the Apple Menu as above for any reason but you know you were working in any of the above apps and more – it’s always worth looking for this menu item.
Extra: How to show the User Library Folder in macOS Sierra — Apple likes to hide this as, be warned, it’s not something you should ever play with unless you really know what you’re doing. So this was well-intentioned, but frustrating for longtime Mac power users. There were still several workarounds to access or unhide the Library folder, but they weren’t immediately obvious or simple (like holding down the Option key when you drop the Go menu in the Finder).
Apple still hides the user’s Library folder by default, but in Sierra you can restore it with a single checkbox: launch Finder and navigate to your user Home folder (you can jump directly to your user folder by select Go>Home from the Finder’s menu bar or using the keyboard shortcut Shift-Command-H).
With your Home folder open, go to View > Show View Options from the menu bar, or use the keyboard shortcut Command-J.
At the bottom of the View Options window, check the box labeled Show Library Folder and then close the window with the red close button in the upper-left. You’ll now see your Library folder listed inside your Home folder, where it will remain unless you uncheck the aforementioned option.
(The handiest thing about this for non-pro users is being able to add your own picture the the Desktop Pictures folder so you can set your own pictures via System Preferences.)