Do sloping greens confuse you?
The first lesson you need to learn is that every putt is a straight putt. That means that even on a sloping green you need to putt to a point straight ahead of you where the ball will break down towards the hole. Once you grasp this concept putting on undulating surfaces will be much easier.
Not sure how it works? Rudding Park professional Mark Moore has a game you can use on the practice putting green to develop your skills.
Watch this green reading video lesson to help.