Part of being a good putter is having your shoulders, arms, hands and the club all working together as a unit. A good way to practice getting that one-piece motion is to use the vice grip drill.
Take your setup, and when you’re over the ball, take your right arm off the club and put it against the left forearm or vice versa. The goal is to lock everything in so that when you hit the putt, you’re able to feel your shoulders, arms and hands working at the same time at the same speed.