I hold the wheel at roughly 9 and 3, thumbs upward and without gripping the wheel hard. I usually don't have to shuffle steer, but if the corner is tight enough I will. A piece of white tape on the top of the wheel serves as a good reference.
Watch the in car video at this page. It is the red 67 911 that was in the August edition of Excellence.
http://www.vararacing.com/Videos1.html