Place the corner heel of your non-dominant hand on top of the club near the edge of the grip. The left hand is the non-dominant hand for right-handed golfers and the right hand is non-dominant for left-handers. Grasp the club lightly along your base knuckles or diagonally across your fingers, whichever works best for you. Either way, the middle of your wrist joint should be on top of the shaft. Keep your index finger loose, allowing the other three fingers to control the club along with the middle two fingers of your dominant hand.
Cover the thumb of your non-dominant hand while placing your dominant hand on the grip closer to the clubhead. Grip the club along your base knuckles or diagonally across your fingers, whichever works best for you. Apply light pressure with the middle two fingers of this hand. The "V" that is formed by the thumb and forefinger of each hand should point just inside your trailing shoulder as you set up to hit the ball. That should reduce the risk of slicing your shot.
Since the index finger of the non-dominant hand is kept loose, many golfers place the pinkie finger of their dominant hand into the space between the index finger and the middle finger. This overlap grip, also called the Vardon grip, tends to work well for golfers with larger hands. It requires more strength to control the weight of the club but it affords maximize control of the clubhead.
Some of the sport's all-time greats -- like Jack Nicklaus, Tiger Woods and Rory McIroy -- prefer to interlock the pinkie finger of their dominant hand with the index finger of the other hand. This grip pulls the hands tightly together and ensures that they work in unison during the swing. The interlock grip works well for golfers with smaller hands, helping them maintain a firm grip without lots of hand and forearm tension.
Some beginning golfers and junior players prefer to grasp the club with two hands, like a baseball bat, with the grip of the club at the base of their fingers. The dominant hand covers up the thumb of the other hand. The knuckles on your right and left hand are lined up together. This grip makes it easier to swing with power but more difficult to control the clubhead upon impact.