Changing sound options doesn't require a trip to the System Preferences. Do it all from the Sound menu, with an Option-click.
Option-click speaker icon in menu bar to choose Mac’s input and output sound sources
Bring back the scroll bars
Scroll bars should show! They're important indicators of how much material remains unviewed. Apple turned them off; we're turning them back on.
Set priority for WiFi networks so your Mac joins the right one
You can set the priority for WiFi networks! This way, you always join the right one, not some sketchy free, open network.
Too many notifications on your Mac? Turn some off.
it's nice to be notified of important stuff but too much is too much! Here's how you customize Notifications, on an app by app basis.
Undo accidental “Move to Trash” on a Mac
Here's how you put a trashed file back where it came from, on a Mac.
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.
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.
Send big attachments using Messages on the Mac, instead of Mail
Use Messages to transfer big files from Mac to Mac. It's not just for sending photos. Send anything. Tell the recipient to drag it to his desktop.
Why does my Mac’s Trash look full even though I emptied it?
The Mac's Trash shows the combined "Trash" folder contents of all disks. If you connect a disk with items you tossed but didn't empty, the Trash fills up.
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.