Here are couple of putting drills that I use with students.
Drill #1 The Ladder Drill
This is to improve your lag putting. You will need 11 tees and four balls for this drill. Find an area on the practice putting green that is level or has a slight grade. Place the tees in the following manner. One tee for a tee box and then step four paces and place two tees a putter length apart and continue this three more times to build four boxes of the ladder. Your objective is lag each ball in succession in the four boxes or you start over. You need to complete this ladder drill three times. This will really help your distance control. Over time continue to move the tee box further away from the ladder as you practice.
Drill #2 The Cross
This drill is to improve your short putting. You will need 12 tees and three balls for this drill. Place the first tee a putter length from the hole and then place the second tee a grip length from that tee and then another tee a grip length from the second tee. It will be a straight line of three tees. Do the same formation all four sides of the hole. The objective is to hole out all twelve putts in succession or you start over. This drill will greatly improve your short putts.