In Windows, I use either the PrintScreen key or the Snip program for screenshots. But I can never remember the keyboard commands for screenshots in OSX, so here is a quick reference:
- Shift Command 3: Capture the whole screen.
- Shift Command 4: Use crosshairs to select an area to capture.
Both of the above methods will save the screenshot on your Desktop.
If I'm working in Firefox, I just use the built-in screenshot tools in Firefox too. (The files are saved in Downloads.)