To be a consistent ball striker, you should strive to swing with a square clubface at all times, unless, of course, you are trying to intentionally curve the ball. Golf is a hard enough game hitting the ball straight, let alone fighting an open or closed clubface at impact.
With a correct grip, your hand and wrist should rotate the clubhead so it stays square to the body throughout the swing. When the club is parallel to the ground, the toe of the club will point up. This is a square clubface. The palm of your right hand and the back of your left hand (if you are right-handed) should end up in what we instructors call the "shake hands" position. As you follow through, again the hands and wrists rotate so that when the club is parallel to the ground once again the toe of the club will point up. Watch this video to check your swing.