One of the biggest aspects that comes up during lessons is how to correctly turn the hips. One of the large contributors to ineffective power and poor contact is the swaying of the hips. When the hips sway too much during the backswing, it can bring your head off the ball causing 'fat' shots and 'thin' shots. It also causes lack of leg drive as the pressure tends to move on the outside of the right foot instead of staying on the inside.
One of the more popular drills to use when establishing correct hip turn is the lawn mower exercise. It involves going into a normal golf posture and positioning your arms in front of your body. You will then place the weight on the inside of your right foot. You then need to imagine as if you're starting a lawn mower and pull the right shoulder back with your right hip.
When performing this exercise, you want to also make sure the left hip is very much staying in the same spot. It can move back an inch or so but in general it will stay in the same position. You also want to make sure the head is stable and on the same angle.
When performing this drill correctly you will feel great turn along with strong resistance from the inside of the right foot. This will create more consistency and power through impact as their will be greater leg drive along with a stable head position.
If you'd like any further help in incorporating this drill into your game, book in for a session.