My favorite lag putting drill is a great drill that helps improve speed control, tempo, and consistency. Take 10 balls on a practice green stand next to a hole and put a tee in the ground about 30 feet away. Hit your first putt trying to get it as close to the tee as possible, then working backwards try and hit a putt 12 inches short of the last one until you hit each ball. Then go to the shortest ball and putt back to the hole you stood by.