Mac Screen Capture shortcuts

Here's how:

To capture the entire desktop, press command-shift-3. The screen shot is automatically saved as a PNG file on your desktop.
To copy the entire desktop, press command-control-shift-3. The screen shot'll be placed on your clipboard for your paste into another program.

To capture a portion of the desktop, press command-shift-4. A cross-hair cursor would appear and you can click and drag to select the area of your wish to capture. When you release the mouse button, the screen shot'll be automatically saved as a PNG file on your desktop. (The file is saved as PDF in Mac OS 10.3 and earlier.)

To capture a specific application windows, press COMMAND-SHIFT-4, then press the Spacebar. The cursor would change to a camera, and you can move it around the screen. As you move the cursor through an application window, the window would be highlighted. The entire window does not need to is visible for your to capture it. When you had the cursor over a window you want to capture, just click the mouse button and the screen shot would be saved As a PNG file on your desktop. (The file is saved as PDF in Mac OS 10.3 and earlier.)

Add Control to the-the-above-to-place the shortcuts-shot on the clipboard instead of saving it to the desktop.

REF:

Http://graphicssoft.about.com/od/screencapturemac/ht/macscreenshot.htm

Mac Screen Capture shortcuts