Over the years of giving golf instruction, I have given my students many different types of drills to help them improve their golf game. I always tell my students, in order to change your swing, you must practice the correct way.  

When you are trying to change your swing, it is important to develop some muscle memory that is different than what you have been currently doing. The best way to accomplish this is by executing a different type of movement. You can do this by practicing a certain drill or by practicing in front of a mirror. Going in a slower motion and swinging the correct way will develop a more consistent and hopefully a better swinging motion.

If you take a lesson and are given a drill, make sure you practice that drill to improve what your body is used to doing. If you continue to hit balls and not change, your bad habits will take over and you will go back to what your body felt comfortable doing before. I believe good practice involves training your muscles correctly without hitting any golf balls.  

Practice does not make perfect. Perfect practice makes perfect.