Imagine you have a swing that produces the following situation. 

• Club face open
• Steep arm movements
• Cast sequence
• Body stalls through impact
• Flip release

You may have a hard time deciding where to start, but if you think about what each movement does to the face and path then the answer might be easier than you think. If a golfer needs to work on shaft rotation, I almost always start with it early in the learning process.