Mac users, if you know only four keyboard shortcuts, let them be these four! Command-Z, Command-X, Command-C, and Command-V are what make the Mac the Mac.
Essential Mac keyboard shortcuts: Command-Z, -X, -C, and -V
Add the Shift key to go the other way
In a spreadsheet, tabbing goes forward... but Shift-tabbing goes backward! Also works in dialog boxes and web forms.
Toggle between normal view and inverted view
If your Mac's screen is white text on black, instead of black text on white, you may be in "Inverted" screen mode. Here's how you toggle that on and off.
Use Escape key to click the “Cancel” button
Quit mousing around! Tap the "Esc" key (Escape) whenever you want to click a "Cancel" button. Quick and easy, never fails.
Hold Command key to see file path in Mac’s Spotlight
Spotlight is great, it finds stuff for you. But when you want to know where the things it found are, it falls short. Unless you use the Command key!
Essential Mac Keyboard Shortcuts: Command-A for “Select All”
The 60 seconds it takes to learn this shortcut will be paid back thousands of times. You have to know Command-A for Select All. Practice!
Essential Mac Keyboard Shortcuts: Use Spacebar to pause/resume audio and video in iTunes and YouTube
Use the space bar to quickly pause audio (or video) in a variety of Mac apps. Tap it again to start it again. Very handy.
Stuff the cat did: toggled VoiceOver so my Mac started talking
Your Mac can talk to you, telling you which button you're about to click, which menus are showing, and so on. Very handy if you can't see well, but very surprising to have it turned on by itself. Or by the cat.
Hide and Show the Mac’s Dock, from the keyboard
Great time-saving shortcut: Command-Option-D to show and hide the Dock on your Mac. Show it when you need it, hide it when you can.
Mac keyboard shortcut symbols, explained
Here's what those mysterious symbols mean in the Mac's menus. When I first got a Mac I didn't know. Maybe you still don't. But now you do.