Okay, I am just going to copy-paste a post from another website and then just credit the author here.
⌘ = Command, the most common modifier.
⌥ = Option or Alt.
⇧ = Shift
^ = Control. Not used as frequently but is still there.
Basic ones…
⌘ + Q = Quit
⌘ + W = Close window
⌘ + O = Open a file in your application
⌘ + P = Print
⌘ + C = Copy
⌘ + V = Paste
⌘ + X = Cut
⌘ + S = Save
⌘ + Z = Undo
⌘ + A = Select All
⌘ + Y or Space = Quicklook
⌘ + Tab = Cycle through windows
⌘ + W = Close window
⌘ + O = Open a file in your application
⌘ + P = Print
⌘ + C = Copy
⌘ + V = Paste
⌘ + X = Cut
⌘ + S = Save
⌘ + Z = Undo
⌘ + A = Select All
⌘ + Y or Space = Quicklook
⌘ + Tab = Cycle through windows
And the rest of it….
⌘ + ⇧+ 3 = Take fullscreen picture
⌘ + ⇧ + 4 = Take selected area screenshot
⌘ + ⇧ + 4 + Space = Take screenshot of window or menu
⌥ + ⌘ + Escape = Bring up Force Quit window
⌘ + Space = Spotlight search
⌘ + ` (back tick) = Cycle through applications windows
⌘ + . = Cancel operation
⌘ + ⇧ + ? = Open help
⌘ + I = Get Info
⌘ + [ = Go backwards in history in Finder
⌘ + ] = Go forwards in history in Finder
⌘ + Up Arrow = Go to previous folder in hierarchy
⌘ + Down Arrow = Open folder of file in Finder
⌘ + ⌥ + T = Show hide Finder’s toolbar
⌘ + Delete = Move item to Trash
⌘ + ⇧ + Delete = Empty Trash
⌘ + E = Eject disk
⌘ + F = Find
⌘ + G = Next result in Find option
⌘ + H = Hide application
⌘ + M = Minimize
⌘ + N = New window
⌘ + ⌥ + W = Close all windows
⌘ + ⇧ + Z = Redo
⌘ + ⇧ + H = Go to Home folder
⌘ + ⇧ + D = Go to Desktop
⌘ + ⇧ + C = Go to Computer
⌘ + ⇧ + K = Go to Network
⌘ + ⇧ + I = Go to iDisk
⌘ + ⇧ + A = Go to Application
⌘ + ⇧ + U = Go to Utilities
⌘ + ⇧ + G = Go to folder
⇧ + ⌘ + Q = Log out
⇧ + ⌘ + ⌥ + Q = Log out immediately.
⌘ + D = Duplicate in Finder
⌘ + ⌥ + 8 = Turn on Voice Over
⌘ + ⌥ + + = Zoom in (if turned on)
⌘ + ⌥ + – =Zoom Out
⌘ + ⌥ + D = Show/Hide Dock
^ + Eject = Show shutdown dialog
^ + ⌘ + Eject = Close all and restart
⌥ + ⌘ + Eject = Sleep
⌘ + Shift + F = Find file by name
⌘ + R = Refresh widget
⌘ + ⇧ + 4 = Take selected area screenshot
⌘ + ⇧ + 4 + Space = Take screenshot of window or menu
⌥ + ⌘ + Escape = Bring up Force Quit window
⌘ + Space = Spotlight search
⌘ + ` (back tick) = Cycle through applications windows
⌘ + . = Cancel operation
⌘ + ⇧ + ? = Open help
⌘ + I = Get Info
⌘ + [ = Go backwards in history in Finder
⌘ + ] = Go forwards in history in Finder
⌘ + Up Arrow = Go to previous folder in hierarchy
⌘ + Down Arrow = Open folder of file in Finder
⌘ + ⌥ + T = Show hide Finder’s toolbar
⌘ + Delete = Move item to Trash
⌘ + ⇧ + Delete = Empty Trash
⌘ + E = Eject disk
⌘ + F = Find
⌘ + G = Next result in Find option
⌘ + H = Hide application
⌘ + M = Minimize
⌘ + N = New window
⌘ + ⌥ + W = Close all windows
⌘ + ⇧ + Z = Redo
⌘ + ⇧ + H = Go to Home folder
⌘ + ⇧ + D = Go to Desktop
⌘ + ⇧ + C = Go to Computer
⌘ + ⇧ + K = Go to Network
⌘ + ⇧ + I = Go to iDisk
⌘ + ⇧ + A = Go to Application
⌘ + ⇧ + U = Go to Utilities
⌘ + ⇧ + G = Go to folder
⇧ + ⌘ + Q = Log out
⇧ + ⌘ + ⌥ + Q = Log out immediately.
⌘ + D = Duplicate in Finder
⌘ + ⌥ + 8 = Turn on Voice Over
⌘ + ⌥ + + = Zoom in (if turned on)
⌘ + ⌥ + – =Zoom Out
⌘ + ⌥ + D = Show/Hide Dock
^ + Eject = Show shutdown dialog
^ + ⌘ + Eject = Close all and restart
⌥ + ⌘ + Eject = Sleep
⌘ + Shift + F = Find file by name
⌘ + R = Refresh widget
Seriously, thanks to http://www.mactricksandtips.com
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