I'm no instructor, and by no means a good snowboarder, but I was always taught that you should keep your weight and stance centered above your board, and your knees bent!!!!!
I'm not sure what you mean by rotating hips????? As your hips should be aligned with the nose and tail of the board!!!!!
* This applies to learning to carve and hold an edge properly on hard pack groomers!!!!! Pow can be a different story!!!!!