The purpose of a golf grip is very simple – to help you keep a firm hold on the club during your swing with as little tension as possible. How it accomplishes that goal – and how it affects your swinging motion – is more complex. The grip is your only contact with the club. You must understand what a grip can and can't do, and how to get the most from it.
Among professionals, the most common of the three primary ways to hold a club is the overlap grip, also called a Vardon grip, after six-time British Open champion Harry Vardon. In the overlap grip, the right pinky overlaps the left forefinger (for right-handed golfers), which helps unify the hands. This puts the wrists close together on the club's grip so they can work more easily as a unit, and the lets the golfer hold the club with his fingers. By doing so, the golfer is able to cock the wrists more easily, which lets him create more clubhead speed. Jim Furyk is notable for using a double-overlap, with the right pinky and ring fingers overlapping the left middle and forefinger, but this is highly unusual.
The interlocking grip has been used by some of the most dominating players ever to play the game. Bobby Jones used it; Jack Nicklaus copied it from him; Tiger Woods copied it from Jack; and many other players have copied them. In this grip, the right pinky locks around the left forefinger. Some players believe this reduces the amount of club speed you can create, but Jones, Nicklaus and Woods are all considered power players. Players with small hands often use this grip.
In the 10-finger or baseball grip, all of the golfer's fingers are on the club, as if he were holding a baseball bat. It's rarely used by the pros, but LPGA Hall of Famer Beth Daniel, Masters champion Art Wall Jr. and PGA Tour pro Bob Estes are among the notable players who have used it. The 10-finger hold, though, is popular among weekend golfers because it's a natural way to hold the club. It also provides a firmer grip for players with smaller and weaker hands. As long as there is no gap between the hands, the 10-finger grip can be very effective.
In addition to technique, the other primary consideration of a grip is the positions of the hands on the club. In a neutral grip, both thumbs are on top of the club; many pros hold the club this way. In a "strong" grip, the both hands are turned a bit to the right (clockwise). That's the most common grip because it makes it easier to square up the clubface at impact. In a "weak" grip, both hands are turned a bit to the left (counterclockwise).
The V formed by your the thumb and forefinger of both hands is a good indicator of grip strength. In a neutral grip, the V's point between your chin and right shoulder. In a strong grip, they point toward your right shoulder, while in a weak grip, they point more toward your chin.