Windows

7 or 8

1. Press the windows key and s simultaneously
2. Type "snipping"
3. The snipping tool application's icon should appear
4. Press "new" and select the area to copy
5. Optionally annotate the image with the drawing tools
6. Choose "Save" (Disc icon) to save as a file or "Email" (Letter icon) to send as an email

3.11, 95, NT, 98, ME, 2000, XP

1. Open Paint
2. Switch to application to be captured
3. Press alt and printscreen (aka prtscr) simultaneously
4. Switch to Paint
5. Press control and v simultaneously
6. Save the image.

Mac

1. Open Preview
2. Choose one of the options from "File > Take Screenshot"

Linux

X11 with Imagemagick

1. Open a terminal
2. To capture a window
1. import outputfile.png
2. Click the window to be captured
3. To capture the whole screen
1. import -win root outputfile.png

X11 basic

1. Open a terminal
2. To capture a window
1. xwd -out outputfile.xwd
2. Click the window to be captured
3. To capture the whole screen
1. xwd -root -out outputfile.xwd