The goal of any good golf swing is to deliver the clubface square at impact. But few amateurs know how to do that consistently. Learn to do it, and you control the ball.
Here's a visual concept that will help you: Take your normal grip with your driver and address a ball on a tee. Now open your right hand and rest it along the shaft so the palm is facing the target and your fingers are pointed down. Notice how the palm mirrors the angle of the clubface.
When you take the club back, let the palm go for a ride in that position, resting against the shaft. If you let the clubface rotate naturally, the palm moves underneath the shaft as you swing the club to the top. On the way down, the palm gradually rotates back to impact, occupying the same position it held at address. Keep in mind, the right palm mirrors the clubface: Square up the hand, and you'll square up the face. Rehearse this a few times, keeping an eye on the palm.
Understanding the relationship between the right palm and the clubface is a great way to fix a slice—it encourages the club to come down inside on a shallower plane, helping to produce a draw.