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.
Hide and Show the Mac’s Dock, from the keyboard
Escape from the Mac’s full-screen mode
Sometimes Apple's changes to the user interface aren't "improvements." For example, putting you in full-screen mode when you click the zoom button. Here's how you escape from full-screen mode.
Force-quit a stuck Mac app, from the keyboard
Here's how you force-quit a Mac app, from the keyboard. This will come in handy some day.
Undo accidental “Move to Trash” on a Mac
Here's how you put a trashed file back where it came from, on a Mac.
⌘-click to open links in new tabs in Mac browsers
Tabbed browser pages are a big efficiency booster. It's all in the Command-key: Command-click to load the link in a new tab, in the background.
Set paragraph alignment from the keyboard in Microsoft Word on a Mac
You can do centered, left justified, right justified, and fully justified, all from the keyboard, in Microsoft Word on a Mac.
How to navigate Mac dialog boxes from the keyboard
Save time by using the keyboard to navigate Mac dialog boxes, rather than the mouse. Try it a few times and you'll be hooked.
Use the spacebar to scroll down in web pages on a Mac
When browsing web pages, tapping the spacebar scrolls you down one screenful. Shift-spacebar scrolls you back up. This works in Safari, Firefox, and Chrome. Way easier than using the mouse or trackpad.
How to type a checkmark on a Mac
You'll need to type a checkmark someday. Here's how to do it.
Speed up your typing with Text Substitution on a Mac
Make your own shortcuts for text you type a lot. Boilerplate text, phone numbers, email addresses, website addresses-- these are great candidates.