The Compass Drill for putting will lower your scores if you practice what it is teaching.
On a practice putting green find a hole that has a slight slope. Imagine that there is a compass over the hole that has 4 lines pointing to north, east, south, and west. Starting at the north line one foot out from the hole. Sink one putt. Once you have made a putt, place a ball at the east line at one foot (clockwise rotation) and make a putt. If you miss this putt, you need to start over at the north, one foot distance.
Once you make a one foot putt from north, east, south, and west locations, start the ball on the north line from 2 foot. Again, any missed putts and you need to start over at the one foot north location.
At first this seems too easy, but it designed to be, after all the first 12 puts are from only 3 feet away. Once you get to the 4 foot distance it should start to get progressively harder, with the slope coming into play as well as the grain of the green etc.
The challenge is to increment out by a foot each cycle and complete 10 cycles of putts without missing one. That would be 40 putts ranging from 1 - 10 feet from every point on the compass. If you can complete that, you are a master putter.
This drill is a great way to quickly get the feel for the greens before going out for a round of golf. By having to start over if a putt is missed, it also helps build confidence that the "gimme" range putts, really should be gimmes and if someone makes you put a side hill 3 footer, you won't hesitate, because you have already hit that on the practice green multiple times before going out that day.
Phil Michelson is said to practice with a drill similar to this one throughout the year. He has practice sessions where he literally putts for hours at a time. If it is good enough for Phil, it is good enough for you.