in-game, use the print screen button, or type /screenshot_ and you'll get a list of options.
The two you'll probably use the most are as follows:
/screenshot_jpg (takes a screenshot without the UI)
/screenshot_ui_jpg (takes a screenshot with the UI. this is useful if you want to show something like PVP scores)
The best way I found the get a great pic of your character is to crank your vid settings to the very top. (a bit laggy for me) go into the tailor and hit printscreen. it will take a pic without any of the UI. Use mouse to zoom in on the face. The JPG will be EXTREMELY detailed. For my ship i do the same. Except I go find a nice nebula in a system with nobody else in it. I position the ship exactly where i want it in the shot. Crank everything up again. Take your snapshot.