Err... judge with your eye?? :bsmilie:
Actually there's no right or wrong way to use the circular polariser. But from the very limited photography knowledge that I know of, you can use blue colour as the guideline for the desired effects. Turn the right around slightly, left and right, and judge for yourself what kind of effect you want. Some may saw 90 degree to the sun, but no one is going to bring a geometric equipment to measure that right? :dunno: