Originally Posted by DiapDealer
Volume-down + Power simultaneously until camera-shutter sound and brief preview of image flashes on the screen.
The images can be found in the Pictures folder (not Photos) in a "Screenshots" subfolder. They will be named in a Screenshot_yyyy-mm-dd-hh-mm-ss.png format.
/sdcard/Pictures/Screenshots when using an android file manager app like ES File Explorer and Kindle\Internal storage\Pictures\Screenshots when connected to a Windows PC via USB.
It finally worked for me. I must have been pressing Volume UP when it did not work.