To take a screenshot, press command-shift-3 to capture the full screen area. To capture a smaller area you define, press command-shift-4 then release all three keys and drag a box around what you want to capture. The image will appear on your Desktop as a PNG file. Pro tip: If you want to capture all the contents of a window without having to drag a box around it, press command-shift-4, release those keys, press spacebar once, then click on the window you want to capture.
