Mac OS X Snow Leopard (10.6) and earlier:

To take a screen shot of the entire screen, hold down the Command (the key with the cloverleaf on it), Shift, and 3 keys.

If you want to select a portion of the screen to capture, hold down the Command, Shift, and 4 keys. If you immediately hit the Spacebar after that, a camera appears that allows you to take a screen shot of any open window.

Mac OS X Lion (10.7) through Yosemite (10.10):

The key commands from prior versions of OS X can be used to take screenshots, or partial screenshots (see above).

In all cases, the screenshot will be saved to the Desktop.

These versions of OS X also allow you to get screenshots using Preview:
1) Launch Preview in the Applications folder.
2) Under the “File” menu, click on “Take Screen Shot.” There are then three options:

  • Selection – functions like Command+Shift+4 on earlier versions.
  • Window – functions like Command+Shift+4+Space on earlier versions.
  • Entire Screen – captures the entire screen, functioning like Command+Shift+3 on earlier versions.

 

Windows XP/Vista/7:

To copy the entire screen, just press the Print Screen key.

To copy only the open window, click on the window and then press and hold the Alt and Print Screen keys.

If you want to save it in a Word file, open the file and then paste the image by pressing both the Control and V keys.