I've thought a lot about this topic for several years. GS8 is easily 'annoyed', and then becomes disruptive at school. Those are the things I've been most concerned about when preparing him for the journey.
But to get him started on the right path, I've had to prepare the journey for him, a lot! His emotional responses are a part of him, his behavior is an outward response to inward feelings. If he can't take responsibility for his behavior yet, then I think I should step in, take that responsibility for a while as I hand it back to him. Kriston presented a good example, if GS(then 5) hit a child(actually I should say WHEN GS hit a child), I would step in, tell him that was not appropriate and ask him to apologize. If he couldn't take responsibility for his behavior, I would apologize for him, then remove him from those situations until he could behave appropriately. To some extent, I think that's preparing the child, but also preparing the journey for the child.

A runner has to work, train, and build up to running a marathon, and I see myself as GS8's trainer for this part of his journey. He doesn't know what I know and it's my job to prepare him. At 8, I'm responsible for this part of his journey. At 18, I expect him to be responsible for the majority of his journey. At that point, I hope to be just a trusted advisor.