We all are aware of taking snapshots in Windows, but when it comes to Mac, we need to stop and think...
Here are few tips to capture screen shots for Mac users.
To take a screen shot of entire screen press Command + Shift Key + 3
For just a portion of the screen, press Command + Shift key + 4, cursor will change into crosshairs, now you can use to select whatever portion of your display you'd like to capture in a screen shot.
If you hit the spacebar after typing Command + Shift key + 4, cursor will replace by camera. With camera, you can take a screen shot of the Dock, the entire menu bar, a single open menu, the desktop, or any open window.