The goal is a really great book, not only do you get the lean approach to running a business but also the approach that the mentor character takes to teaching is one that seems really effective. He always answers questions with more questions forcing the main character to really think about what the answers to his own problems are.
Upon further research this approach appears to be based upon the Socratic Method, by Socrates who was born in 470BC. So why have we adopted it so little? I guess it because it is very hard to retrain yourself to ask questions instead of give answers, maybe there is something satisfying in appearing smart because you know the answer. But there is surely more value in asking the correct questions, the learner will start to develop better analytical patterns to follow when they have questions, and this should free up time for the teacher as much less explanation is required.
But what questions should you ask as the teacher, one question suggested by a colleague of mine when a junior team member approaches them is to ask them what they have tried so far, this seems to be a good starting point. From here do we ask them a question to highlight the area they should be looking at or do we ask a question to get them to think about the different areas the problem could be in. I would suggest the latter as surely the goal of teaching is to make the student independent of the teacher.
Time to read some plato I think!