The most common error I see golfers make in their putting fundamentals is where they have their hands in relation to their putter-head and shoulders.
In the picture below you can see this amateur has his hands what I call “low” highlighted in red. This is common in golfers because every other shot that we take in golf we set up with out hands “low”. This player was able to decrease his skid distance (the amount the ball skids before beginning to roll) which increased the players’ ability to control speed!