Here are some frequently used shortcuts that will save you time on your OS X Mac:

+a = select all
+b = bold
+c = copy
+d = duplicate
+e = eject
+f = find
+g = find again
+h = hide window
+i = italicize/show information
+l = create alias
+n = new
+o = open
+p = print
+q = quit
+r = refresh web page
+s = save
shift++s = save as
+t = new tab in Firefox
+v = paste
+w = close the window
+x = cut
+y = redo
+z = undo
+delete = move to trash
ctrl+click = right-click
option++8 = turn on zooming
option+++ = zoom in
option++- = zoom out
+option+esc = force quit
power button+enter = shut down (wait for box before pressing enter)

There are many more shortcuts than those listed above, and each program contains its own unique set of shortcuts.  A more extensive set of shortcuts can be found at http://docs.info.apple.com/article.html?artnum=7545.

• The format of the above (i.e. "+z = undo") can be executed as follows: Hold down the "command" (Apple) key first, and while still holding it down hold down the "z" key.  You must then let go of the two keys simultaneously in order to get the desired result, which in this case would be to undo the last action you performed.
• The key is known as the “command” or "open apple" key.
  
• These shortcuts will only work if you are using OS X.