Question: How can I take a screenshot in X.org?

I am unsure if the Print Screen button will "just work" and I don't know how I would go about testing it.

Answer: 
The most commonly used Linux application for taking screen-shots is called `scrot`

You can install it with for Debian:

`sudo apt-get install scrot`

Or for Arch:

`sudo pacman -S scrot`

A screenshot is taken by typing:

`scrot output-file.png`

If you want to bind `scrot` to the `print screen` key then that will need to be controlled by your window manager.
I use 'xwd'. For example, one I just did: `xwd | xwdtopnm > dw.ppm`
The only downside I know of with xwd is that you need some other utility to convert its output to something understood by anything other than 'xwud'.