You will often hear golf professionals talk about the body as the engine of the swing but what exactly do we mean? To create effortless power, your upper body needs to turn against your lower body. This means that at the top of the backswing your back should be facing the target while your hips will have only rotated about 45 degrees.
Of course, this is just a guide, as the amount you are able to turn will depend on your flexibility but this should still give you an idea of the basic principle we are talking about here. The difference between the amount of turn in your upper body versus a stable lower body creates torque. This is stored energy that will add speed to your downswing.
I see a lot of players who, on the face of it complete their backswings but on closer inspection are only swinging their arms - the upper body is not turning against the lower body. This is a weak position that is doing nothing to help you hit your power potential.
Try placing the shaft of your driver across your shoulders and make your normal backswing. Depending on your level of flexibility the butt of the grip should point to the right of the ball (as you look) and not to the left. A good test to see if you are creating resistance is to hold this position for a few seconds. If it's hard to hold, you are producing and storing power for later in the swing. If you feel no tension, a lack of resistance is costing you power.
If you are worried that you aren't hitting your power potential visit your local Foremost Golf professional for advice. Good, solid mechanics will help you hit the ball both longer and straighter and I am always here to help you improve.