The key to those extra yards you're seeking is often not more clubhead speed, but more effective clubhead speed. Consciously trying to "hit the ball hard" can lead to a quick move from the top, causing your clubhead speed to peak too early.
To ensure that the clubhead moves fastest at the ball instead of before it, focus on the finish instead of impact. Keep your momentum going well into the follow-through—you want to finish with your arms wrapped around your neck and your right shoulder closer to the target than your left.
A full finish eliminates the "hit impulse," enabling you to build clubhead speed more naturally and gradually and to make the most of your power potential.