There are many keyboard shortcuts that are commonly available in many applications. Using the keyboard shortcut to accomplish a task is quicker since the user doesn’t have to spend the time clicking in multiple menus to complete the task at hand. For example, pressing the Alt key and the S key at the same time will save data. This is generally displayed in instructions as “Alt + S.” Pressing “Ctrl + C” will copy data (can be text, a picture, table, etc.). Pressing “Ctrl +V” will paste the copied data. Printing is another common task that has a shortcut. “Ctrl + P” will print your document. Keyboard shortcuts can be the ultimate timesaver if the user remembers & knows how to use them. 
Although many PC keyboard shortcuts are the same for Mac operating systems, there are also many diffrences in shortcuts between the two. These are some examples of Mac operating system keyboard shortcuts:Shift-Command-A Open the Applications folder, Command-C Copy selected item/text to the Clipboard,Shift-Command-C Open the Computer window, Command-D Duplicate selected item, Shift-Command-D Open desktop folder, Command-E Eject,Command-F Find any matching Spotlight attribute, Shift-Command-F Find Spotlight file name matches, Option-Command-F Navigate to the search field in an already-open Spotlight window,
Shift-Command-G Go to Folder,Shift-Command-H Open the Home folder of the currently logged-in user account, Command-I Get Info, Option-Command-I Show Inspector, Control-Command-I Get Summary Info, Shift-Command-I Open iDisk, Command-J Show View Options,Command-K Connect to Server,Shift-Command-K Open Network window,Command-L Make alias of the selected item. 
- All information can be found in Chapter 6 of Understanding Computers Today and Tomorrow, 13th Edition by Deborah Morley & Charles S. Parker.
- All information can be found at http://support.apple.com/kb/HT1343