Almost all professionals use a putter with a flat fronted grip. It encourages the correct hold: thumbs to the front and hands to the side. The rules say that there must be at least 10 degrees between the putter shaft and the vertical. This is to stop players from using a croquet type action, facing the hole.Theoretically, the more upright your putter sits, the easier it is to swing back and through on a straight line with a hinge action. If you have a putter that sits flat, you will tend to swing it around in a curve. So upright is generally easiest.Always check the sweet spot on the putter. That is the hitting area on the clubface that will give you a reliable strike. To see just how good it is, hold the putter up loosely from the top of the shaft with your left hand and start tapping along the face from the toe with a coin or fingernail.Tap at the toe, and you will feel it twist. Gradually work toward the middle of the face, and you will feel it wanting to swing back and through with no twist. Tap again toward the heel, and you will feel it twist once more. The bigger the area with no twist, the easier the putter is to use.Mark the centre of the sweet spot and aim to hit the ball from this. Marks put on by the manufacturers do not always correspond with the sweet spot. Check this before buying one.Putters basically fall into four designs the blade, the mallet. the centre shaft and the heel to toe weighted putt. The last two are likely to have the largest sweet spots. By comparison with these, the old-fashioned blade putter can be difficult to use.The length of putters varies from about 32 inches to 36 inches. If your putter is too long, the temptation is to hold it at the top of the shaft and over bend the wrists. Good putting requires the left wrist to ride high. The correct length of shaft will encourage this.Putters vary slightly in loft from 3 degrees to about 7 degrees. Those with very little loft are ideal for tournament greens. Those with more loft can be useful on bad greens and for players who press their hands forward at address. A light putter can be very difficult to control, while a heavy putter tends to encourage a smooth swing.