To take a screen shot with Mac OS X hold down the Command (cmd) key and the shift key and either the number 3 to take a shot of the whole screen or number 4 to change your pointer to cross-hairs that can be dragged across a section of the screen to capture just tat part. With the cmd+shift+4 option you can put your pointer over a window and press the space bar to capture that window,

In the Utilities folder which is in the Applications folder is software called Grab which does the same thing but also allows for a delayed capture which gives you ten seconds to arrange your screen before taking the shot.