In this video, Golf Fitness Specialist Dick Bartling gives you an exercise to help with core stability.  Start off in the plank position with your weight on your elbows and toes. Try to hold this position for up to a minute with not too much shaking in your abdominals. Keep your back flat with no arches up or down.  If you would like to advance the exercise you can put one arm up and out at a time.  Once you have got that down, try to put one leg out at a time. Ultimately you are trying to get to having one arm and one leg off of the ground at the same time, while still maintaining your core stability.

For a great tip on how to improve hip rotation, click here.