When i hit F12, my throttle goes to 1/3, and no screenshot is taken. Am i hitting the wrong key to take screenshots?

ECD

Yep

When you not in the Flight Engine you need to press ALT-O and a BMP named "Frontscreeen#.BMP" will be created in you XWA directory

TO do so while Flying you need to use CONTROL-Printscreen. And a BMP called "Flightscreen#.BMP" will be created in your XWA directory

F12 and F11 are power Pre-sets that you can configure in you general Options