One of the least known keyboard commands on the Macintosh is the built-in features of Mac OS X to take a screenshot of the screen.  While the shortcuts are second nature to me, I often find that people are not aware of them.  So here is a quick summary of the how to take a screenshot:

1. Take a picture of an area of the screen.  This is by far my favorite shortcut.  If you press Command + shift + 4 you can select the area of the screen that you want to take a picture of.   By default it will save the image to your desktop but you can change the default destination.  Now, some extra great features for Leopard users follow:
   1. Command + shift + 4 and then press your space bar to capture the window that is directly under the cursor.  This is the easiest, and most often used by myself.
   2. Command + shift + 4 will by default allow you to select an area on the screen, by holding the space bar, you will lock the size of the window, but be allowed to drag the capture window around.
   3. Command + shift + 4 and the Option key will allow you to area you have selected bigger by expanding all sides from the center.
   4. Command + shift + 4 and then the shift key again will allow you to resize one edge of the selected area.
   5. Shift + control + command +4 will take a screenshot of a selected area and copy it to the clipboard.
2. Take a picture of your whole screen.   If you pressCommand + shift + 3 your current screen will be captured and saved to your default folder.
3. You can change the default format of screenshots. By default the format of screenshots are dependent on the OS.  Typically in 10.5 & 10.6, screen capture is saved as a PNG file.   You can however change the default format by doing the following:
   • Open up a Terminal (Applications>>Utilities>>Terminal).
   • Type the following code at the prompt:

   defaults write com.apple.screencapture type jpg
   killall SystemUIServer

4. You can use the Preview application.  You can also take a screenshot by opening up the standard Mac Preview application (Applications>>Preview).  You get all the options mentioned above.  Open up the application, go to the File menu and select Take Screen Shot (pick full screen, partial area, or window).  It’s really that simple.
5. For the advanced user, you can use the QuickTime Player in Snow Leopard, to make a screen movie.  This is a video capture of what is on the screen, and is completely free.  You can choose to capture the Audio at the same time, or you could use Use iMovie, or QuickTime player to create an audio track and merge the files together, and then have a tutorial video, without spending any money on extra tools.

Another reason that I like this functionality so much is that it is FREE.