In order to return the clubface square at impact and strike the ball in the center of the clubface on a consistent basis, you need to have a proper grip. The clubface is king and it is the primary factor in determining where your ball starts and curves. Your hands are the only connection with the golf club and it is critical that you grip the club correctly to be able to control the clubface.
With the clubface square to target, grip the club in your left hand first (for a right handed player), with the grip laying in the base of your fingers. It is imperative to keep the grip in the fingers to have some leverage and not let the grip lay in the palm. The "V" formed by the left thumb and left index finger should point towards your right shoulder (for a right handed player). You should also be able to see your top two knuckles when looking down on the grip as a good reference point.
The pad under the left thumb goes directly on top of the grip and the left thumb should lay just behind the shaft. Positioning the left thumb here creates a lever and levers are multipliers of power. The position of the left thumb is important as it is the key to rotating the face of the club. Where it is determines how much rotation the face will have. If you have the left thumb directly on top, the face stays open as you apply pressure coming into impact. If you are a slicer of the ball, check this part of your grip and make the adjustment.
Place your right hand on the club keeping it in the fingers. You can interlock your right pinky between your left index finger and middle finger, take a baseball grip with all 10 fingers on the grip or overlap your right pinky on top of the space between your left index finger and middle fingers.
The left thumb should fit perfectly in the palm of the right hand and the right thumb pad lays just on top of the left thumb so that the left thumb is covered. Point the "V" formed by the right index finger and right thumb towards your right shoulder.
The right thumb lays just on the left side of the shaft matching the position of the left thumb on the other side so the hands can work together as a unit and not against each other.
The palms should face each other and neither hand should be turned too far under or over.
Right palm facing ground and overlapping left hand causing grip in left hand to be more in the palm
Palms facing each other
Right palm facing sky, left hand turned downward too much
3 Pressure Points
How tight should you hold the grip? If you squeezed the grip as hard as you could, that would be a 10 out of 10 on a grip pressure scale. A 4 or 5 is ideal for the full swing shots. A 2 is ideal for bunker shots and 7 or 8 is ideal for when the ball is in the heavy rough.
Left hand: Last three fingers
Left thumb sitting in the pad of right palm
Right Hand : Middle two fingers