One of the biggest and most important skills in putting is start direction, in other words, can you start your ball on your intended line? The gate drill is a very simple, yet effective way to hone that skill.
Simply place two tees on either side of a ball that is on your intended line and practice hitting putts between those two tees. You will get immediate feedback if you’re pulling or pushing the ball off the clubface, which will improve your clubface control through impact.