When making the golf swing it is very important to stay connected. The left arm (if you're right handed) should stay touching with your chest on the backswing and down to impact. This will increase both power and accuracy. Keeping connected will reduce the chances of going outside the club plane and hitting a weaker fade or slice. The easiest way to check the swing without becoming disconnected is to put your golf glove under your left arm and hold it there for the backswing all the to the top of the swing to the bottom without letting it fall out until just after impact. This tip will certainly improve your ball striking.