Common Keyboard Shortcuts for Mac OS X Yosemite Created by @Matt425

Startup Shorcuts Application Shortcuts

Option or Alt Display All Startup Volumes Command-Space Show or Hide Spotlight

Shift Startup in Safe Mode Command-Tab Move Forward through Open Apps

C Startup From Bootable Media Command-Shift-Tab Move Backward through Open Apps

T Startup From Target Disk Mode Command-F1 Toggle Mirror Displays

Command-R Use OS X Recovery Command-F2 Toggle Target Display Mode

Command-Option-P-R Reset NVRAM/parameter RAM Command-F3 Show Desktop

Option-F1 or Option-F2 Open “Displays” System Preferences

Taking Screenshots Command-Minus Decrease Size of Selected Item

Command-Shift-3 Capture the Screen to File Command-Shift-Equal Increase Size of Selected Item

Command-Shift-Control-3 Capture the Screen to Clipboard Command-A Select All

Command-Shift-4 Capture Selection to File Command-B Bold

Command-Shift-4 then Space Capture Selected Window to File Command-C Copy

Command-Shift-Control-4 Capture Selection to Clipboard Command-Option-D Show/Hide Dock

Command-Shift-Control-4 then Space Capture Selected Window to Clipboard Command-F Open a Find Window

Command-H Hide Windows of Current App

Text Selection Shortcuts Command-I Italicize

Command+Arrows Select Text Command-M Minimize App

Control-A Move to Beginning Command-N Create New

Control-L Center Command-P Print

Control-O Insert a New Line Command-Q Print

Command-S Save

Keyboard Controls Command-U Underline

Tab Move to Next Item Command-V Paste

Shift+Tab Move to Previous Item Command-Z Undo

Command-Shift-Z Redo

Command ⌘, Control ⌃, Option ⌥, Shift ⇧, Caps Lock ⇪, Function fn Command-Control-Space Special Characters, Smileys, etc.

For a Complete List: http://support.apple.com/kb/HT1343