Many people suffer from a reverse pivot or a poor weight shift. There's one simple drill that will help you "get through" the ball with your weight on your left side.
This drill is borrowed from baseball. Start with your feet together and then swing the club to the top. As you start your downswing, step toward the target with your front foot just as you would to hit a baseball.
Starting with your feet together will ensure that you get your weight onto your front side as you swing through the ball. This drill is also very good to get the feel of the swing starting at the bottom and stop those golfers that cast their hands to start a golf swing. Try this drill without a ball first or until you have mastered the stepping motion with good balance.