As one who works with people needing technical assistance on a regular basis, I understand the value in being able to easily take screenshots of your screen. Not only can this help (tremendously) in the process of troubleshooting an issue, but it's also great for lots of other reasons (training others, creating graphics, etc). Honestly, the possibilities are limitless.
Mac OS X Mountain Lion makes it really easy to capture screenshots in a variety of ways. Below are five methods.
1) Take a picture of the whole screen
Press Command (⌘)-Shift-3. The image is then saved on your Desktop.
2) Take a picture of part of the screen
Press Command (⌘)-Shift-4, and then drag the crosshair pointer to select the area. Continue to press the mouse button, release the keys, and then press Shift, Option, or the Space bar while you drag to resize the selection area. When you are ready to take a picture, release the mouse button. The image is then saved on your Desktop.
To cancel, press Escape before you release the mouse button.
3) Take a picture of a window or the menu bar
Press Command (⌘)-Shift-4, press the Space bar, move the camera pointer over the area to highlight it, and then click. The image is then saved on your Desktop.
To cancel, press Escape before you click.
4) Take a picture of a menu, including the title
Click the menu to display the menu commands, press Command (⌘)-Shift-4, and drag the crosshair pointer over the area. The image is then saved on your Desktop.
To cancel, press Escape before you click.
5) Take a picture of the menu without its title
Click the menu to display the menu commands, press Command (⌘)-Shift-4, press the Space Bar, move the camera pointer over the menu to highlight it, and then click. The image is then saved on your Desktop.
To cancel, press Escape before you click.