The Grab Utility
There is a very good utility in Mac OS X that also lets you capture screenshots, called Grab. You will find Grab in the Applications --> Utilities folder. To take a screenshot with Grab, open the application first and from the Capture menu, choose one of the following capture modes.
The Window mode lets you select the window you wish to capture. When you select the Window mode, a window will open requiring you to choose the window you wish to capture. Click on the Choose Window button and the screenshot will be taken.
This mode lets you capture a specific portion of the desktop by dragging the mouse pointer around it. Grab displays a tooltip showing the size of the area you have selected and as soon as you release the mouse button, the screenshot will be captured and opened in a new window.
If you select the Screen mode, a window will open waiting on you to click anywhere on the screen to take screenshot. In this mode, you can capture anything on the screen that is at the front.
This mode enables you to set up your desktop for timed capture. Click on the Start Timer button and the timer will start. You will then have 10 secs. before the screenshot is taken. In this wait period, you can adjust the screen items, open any menus, etc., to include in the screenshot.