The ideal action that the putter head should take through the golf ball is that of a straight line backwards and forwards directly online with the target.
At the same time the club face should stay 'square' (at 90 dergrees) to the straight line so that the club face never leaves the target. When this occurs, the only possibility is that the ball will travel straight towards wherever the golfer aims - this is the ideal!
To achieve such an action, the vital fundamental is that of the golfer's grip. A poor grip means that a straight putting stroke is unlikely, a solid, correct grip and it becomes a very real possibility.
To check your putting grip is correct we can identify it as 'weak', 'strong' or 'neutral'.
Note - these descriptions all assume the golfer is right handed, reverse the instructions for left handed golfers.
The 'weak' grip
A weak grip is one where the hands are positioned too far to the left of the golf club. The right hand is too far over the top and the left hand is over to the left hand side of the grip. With the hands in this position the whole set up is affected and the shoulders tend to point to the left of the target. With the shoulders pointing in this direction, the swing path of the club head will be directed to swing right to left across the ball causing a pull to the left. The only option for the golfer is to manipulate the hands through the ball to keep the ball on target which causes inconsistency in both distance control and accuracy.
The 'strong' grip
A strong grip is the opposite of the weak grip. The hands are positioned too far to the right of the golf club. The right hand is too far over to the right side and underneath the grip, while the left hand is positioned on the top of the grip. With the hands in this position the whole set up alters and the shoulders tend to point to the right of the target. With the shoulders pointing in this direction the swing path of the club head will swing from left to right across the ball causing a push to the right. Here the golfer will have to adjust the hands through the ball to keep the ball on target that, once again, causes inconsistency in both distance and accuracy.
The 'neutral' grip
The ideal grip that is balanced, symmetrical and where the hands work together. In this grip the palms face each other when positioned on the putter. Both thumbs and index fingers point straight down the club shaft towards the club head with the thumbs positioned on the flat front of the putter grip. This grip allows the golfer to stand side on to the target with the feet and shoulders both in a parallel line to the target. The body and hands can therefore work together to control the face of the putter with the palms and swing the putter online to the target with the shoulders.
To check which grip you have, take a good look when you are set up to the golf ball - even get yourself set up in front of a mirror - and check whether your grip and body position is symmetrical. Use the flat front of the grip as a checkpoint for the thumbs and ensure that the palms are facing each other on either side of the grip.
Use these points to neutralize your grip and your poor putts in one go.