The Clock Face
This game helps you build the confidence you need to hole the short must-makes. Take 12 balls and circle them around the hole about 3 feet out placing them on the numbers of an imaginary clock face. You can vary the distance from the hole a bit to keep it interesting. Play until you knock in 12 in a row. Confidently holing the 3-footers will do wonders for the rest of your game.
Alone or with a buddy, drop five balls in a line about 2 feet from the hole. Putt out and sink them. For every one you miss, place the ball a foot further from the hole, setting it back a foot each time you miss. Do this for three "rounds" or 15 balls with the winner getting a buck.
Pars or Better
Drop a few balls 10 or 12 feet from the hole pretending you are in regulation. Playing one ball at a time, stroke it as if it were for a birdie. If you miss, putt for par making sure to hole out in two. Play 10 times or until you make all birdies and pars.
Closest to the Hole
Set 10 balls about 30 feet from the hole, the length of a long lag putt. Imagine the hole as a bull's eye and score yourself, alone or with a buddy, 0 points for holing out, 1 point for within a foot, 2 points for within 2 feet, 3 points for within 3 feet. All balls outside of 3 feet count as 5. Low score wins.
Set a tee in the green about 6 feet out. Place a second tee on a different line about 20 feet out. Set a third tee about 12 feet out on a different line still. With six balls, putt one to each tee short to long to medium and then repeat it with the second ball. Mixing up the distances and the lines replicates the variety that will greet you on the course and keeps you from becoming too nonchalant about the distance. Award yourself a point for every putt outside of 12 inches and see how low you can go.