You pull three putts in a row, and then push the next two, or some similarly distressing pattern. No matter what you try your putts won't start on line consistently.
Stop putting with the grip you use to hit power shots. You don't want to hit putts. Instead, angle your wrists slightly downward and move the putter grip out of your fingers and into the lifeline of your left hand.
Why it works:
Gripping clubs in your fingers allows your wrists to hinge freely and add power to your swing. That's great for your long game, but not for your putter. On the green, excess power is a big negative, so you should keep your wrist movement to a minimum. When you angle your wrists downward at address and grip your putter under your lefthand lifeline, your putter becomes an extension of your forearms. This neutralizes wrist movement and produces a much smoother putting stroke.
Try this: Use your lifeline
Hold a pencil in your fingers and move your wrist and hand in every direction. It's easy. Now slip it up into the lifeline of your hand and extend it up past your wrist. When you cock your wrist downward to get the pencil parallel to your forearm, the motion of your hand and the pencil becomes restricted. This is the feel you want in your putting stroke.