I have been using a Windows 8 and a Surface RT tablets for a while. Although I do have a small Microsoft Wedge Keyboard and a touch-cover for the Surface RT, many times I just want to capture a screenshot without using a keyboard (and press Windows + PrtScn).
For a Surface RT, you can press and hold Windows Key button and then press the volume down button to capture a screenshot.
But you can also use the snipping tool to do that as well. We start by using the search charm and search for “Snipping Tool.”
Once you have a “Snipping Tool”, you can capture the full-screen snip or you can choose other options.
Hope this helps!