How many times have you come across a situation where you and the other person weren't speaking the same language?  I have worked with a variety of clients, and all in all it's not been easy when people have a different outlook on what you're trying to accomplish, compared to what needs to happen.  How far do you cross the line?  How often do you take the assertive role versus the passive role to get the work done?

It ultimately comes down to a team concept, for both parties to agree upon what is the best course of action and stick to it.  Tweak it as you go along, do a thorough revist every few months, and track your progress.  Above all else, the key is to keep it in writing and make sure that everyone agrees to what needs to happen.  Without this, nothing will be accomplished and you're doomed to failure.  Follow up with e-mails, frequently, and be proactive instead of reactive to the situation.  Unless you're the owner, you are a support mechanism to seeing it become a success.  However from personal experience, when you start becoming emotionally invested in the situation, it's time to back away because you do lose sight of what you've been brought in to do.