How to take screen shots in MAC

• Command-Shift-3: Take a screenshot of the screen, and save it as a file on the desktop
• Command-Shift-4, then select an area: Take a screenshot of an area and save it as a file on the desktop

In Leopard and later, the following keys can be held down while selecting an area (via Command-Shift-4 or Command-Control-Shift-4):

• Space, to lock the size of the selected region and instead move it when the mouse moves
• Shift, to resize only one edge of the selected region
• Option, to resize the selected region with its center as the anchor point