Often I need to create user guides and demo videos for products, and the screen capture features help a lot.

To capture:

- the entire desktop: Command-Shift-3. (Automatically saved as a PNG file on your desktop)

- part of the desktop: Command-Shift-4

- specific application window: Command-Shift-4

Add Control to these shortcuts to place the screenshot on the clipboard. Also try the bundled Grab utility for more related features.