Over Swinging and how we can Fix It.
1st, if you go to a Driving Range with a Friend have them stand behind you and hold an alignment (if you have) off your back shoulder and you want to just want to touch it. At home stand against the wall make a back swing (with just your hands) you want your hand to touch the wall.
Also try this one start at address with a golf club (7or6iron), rest the SHAFT on Back Shoulder, TURN, Lift and push your Hands away from your Head/ shoulders.