To avoid spamming the general screenshot thread with GW2 related pictures, here's a thread dedicated for that purpose. Grab your camera and start taking some pictures! Everything (as long as it's game related) is welcome here.
[Print Screen] = Takes a picture. (Can be rebound in the control options)
You can also bind a key for 3D pictures but I'm afraid only a minority can actually see those properly.
Have a look at the chat to see where the picture was saved. If you forgot, then screens are generally saved to:
[Windows 7] - C:\Users\*Your User Name*\Documents\Guild Wars 2\Screens
[Control]+ [Shift] + [H] = Hides the user interface.
Bind a key for Draw Weapon for some seriously cool shots.
Here's my Guardian: