Mac OSX lets you easily capture screen shots of your entire screen or just a specific window using:
Command + Shift + 4
I use this functionally often and got tired of captures being saved to my desktop (the default). To change you simply run terminal and change the system default:
defaults write com.apple.screencapture location ~/Pictures/Screenshots/
Make sure the directory exists first or it will not work. To have the changes take effect, you then must type:
Another useful trick is to be able to screen cap directly to clipboard and never store the screen shot on your drive. This makes it really easy to paste into documents or e-mails. To do this
Command + Control + Shift + 4 (not f4).
Its a bit hard to execute the keystroke with one hand so you can use two hands then use the mouse to select the area you want to capture.