Get the 1976 Edition!
This book by Carl Wilson is the best work on making disciples that I have seen. He carefully shows how Jesus built disciples by intentionally addressing specific areas of teaching and experience during the time that He taught them. Wilson develops a "harmony" of the Gospels that shows the overall pattern of Jesus' ministry and the effectiveness of His teaching. This approach to discipling emphasizes the importance of delivering adult Christian education in a planned progression of learning experiences rather than the haphazard approach that is promulgated by most curriculum publishers today. If you teach adults (or lead an adult ed program), GET THIS BOOK!
My main piece of advice is this: buy the 1976 edition, NOT the newer 2009 edition. I had first seen a 1976 edition in a library and naively thought the newer edition would be even better. So I purchased the 2009 edition, and I was very disappointed. Wilson has now separated the work into TWO volumes, removing the valuable "harmony" of the Gospels and placing it in a separate (expensive) volume. Since the Gospels provide the underpinning for the method of discipling that Wilson recommends, the omission of that material was a TERRIBLE decision! Again, you're better off purchasing a fine-quality 1976 edition than the newer one. I discarded my 2009 copy and went and bought the 1976 edition -- and it is a great resource.