Yes; the uber-geeks know it. Still there are lots of users who have no idea how to do it. If you are one of those, here is what to do to take a screenshot on Lumia phones:
To take a screenshot on Lumia phones
Press the power button (on the side below the volume buttons) and Start button (the one with the Windows icon on it) together. That takes a screenshot and saves it to your gallery. You can find your screenshots by navigating to: Photos > albums > Screenshots.
It works on any Lumia smartphone. Now, go have fun, people!