Slowly. I use circle templates. The way I do it is to turn the quill as I go around the circle so the nib is always moving in the right direction. Takes a bit of getting used to and does leave ink on the templates that needs to be wiped immediately. But to do it freehand, I always go counterclockwise. If the nib is getting caught in the paper you may be using cheap crappy paper. Try some smooth or the least a vellum finish.
You can also use a tech pen or a ruling pen with a template.