Taking Screenshots in Mac OS X
MacRumors has pretty much everything you need to know. You can also take screenshots remotely, over SSH. (Just remember that with great power, comes great responsibility.) The only thing the built in functionality can’t do is take full screenshots of windows that scroll beyond the screen. There’s tons of commercial apps to do that, but Papparazzi! will do the job for free.
[...] Most adult Windows users who use Microsoft’s Paint actually use it to save screen shots, which is easier in OS X with Preview’s “Grab” menu or keyboard shortcuts. [...]