Let go of the club to unleash your power. The next time you are at the driving range notice how many golfers, no matter what their ability, swing the golf club easy and loose on their practice swings. But, when they step up to hit a shot their swing looks totally different. The reason for this is during their practice swing they hold the club with a relaxed grip and just swing the club through the hitting zone. Tension in their grip takes over when they are hitting the ball. This result is a swing using the large muscles of the upper body and no release of the hands and wrists though the hitting area.
A drill that will help you swing the club like your practice swings and greatly improve your release through the hitting area is to feel like you are going to let go of the club when you are striking the ball. It will be a little scary at first, but just hang in there and practice this when you are at the range, or on the course practicing. You will start to feel your hands and wrist generate more power and speed through the hitting area. This will result in longer and straighter shots, especially of the tee.
A drill that Patty had my wife do when she was first learning was to go to the beach, find a stick about the weight of a club and actually let it go. This will help create the "whip" that generates power.