The game is won or lost on the putting green and being a great putter, capable of holing putts is the difference to whether the score is low or high.

To be able to hole putts you need a reliable, accurate, putting stroke and employing a straight-back-straight-through method when you putt will really help you improve your ability to roll the ball accurately along the target line.
A straight-back-straight-through putting stroke has the putter head moving straight back along the target line and then straight through the ball along the target. If you keep the putter face aiming down the target line as you use this putting style, then the ball will always be hit directly along the target line, resulting in you becoming a very accurate putter and if your distance control is equally as good as your accuracy, you will be holing a lot of putts and therefore taking fewer shots.

To create a straight-back-straight-through putting stroke you need to set up and address the golf ball in a way that allows you to create a pendulum between your arms and the putter. If you consider how a pendulum works, the top of the pendulum is sited directly and vertically above the bottom of the pendulum. In a putting situation, the top of the pendulum is your shoulders and the bottom of the pendulum is the putter head. If the pendulum is set in this way, then it will swing in a straight line and this will produce a putter head that travels straight along the target line, straight-back along the target line as the putter head swings away from the ball on the back swing and then straight-through as the putter head swings through the ball and down the target line towards the target.

To create the movement, the position that you set up in is crucial. You need to create a position where you tilt forward with your spine and upper body so that your arms are able to dangle freely from your body. With your arms in this position hanging vertically under your shoulders, you will be able to swing in a pendulum action. Hold the putter where your hands dangle, even if this is low down on the handle.

You need to set your eyes either over the golf ball, or just inside the golf ball, depending upon the style of putter that you play with and the angle that the shaft comes out of the hosel of the putter head. The more vertical the shaft angle, then more directly you will set your eyes over the ball. Doing this will set your shoulders (the top of the pendulum) effectively in the correct position above the putter, allowing you to swing your arms and the putter so that the putter head swings straight-back-straight-through. Set your feet shoulder width apart and the ball in the middle of your stance and you will now make a really accurate movement along the target line. With the putter face aiming down the target line as you do this, you will hit your putts much more on line and you will see that you hole more, which will lower your score.