Determining the proper length club for a player is one fitting component that is often done incorrectly, resulting in a player using clubs that are either too short or too long. Using a ruler or yardstick to measure wrists or fingertips to floor is an incorrect method, and has little to do in determining the proper club length for an individual. This method doesn't take into consideration a player's ability level or posture when addressing a ball.
A player should use the longest possible length club they can handle that produces consistent center face impact, good directional control and a solid feel at impact. Keep in mind as a club gets longer it is more difficult to hit in the center of the face resulting in a loss of distance and directional control.
Using impact tape on the clubface is the correct method to determine the proper length club for a player. During the process the player is given a progressively longer iron of the same number (i.e. 7 iron) We know we have exceeded their proper club length once the player can no longer produce consistent impact marks near the center of the face.
As you can probably tell by now the biggest factor in determining proper club length is the player's ability. As a player's expertise improves his impact patterns will be more consistent and closer to center.
In regards to the driver it is interesting that a shorter driver length will often increase a player's distance. This is because the ball is struck closer to the center of the clubface applying more energy to the ball. Most weekend players will hit the ball straighter and more consistent using a driver no longer that 44 1/2 inches in length.