Drils to stop leaving putts short

I put a backstop about 3 feet past on a 15 foot uphill putt.

1 point for everything between the hole and the backstop, 3 points for in the hole, 0 for anything short and -1 for anything that hits the backstop.

I use 5 balls and see how well I score, then I try and beat it.

I use similar drills for 20, 30 feet but give a little more room behind if required.