Throw the Rule Book OUT!

There are TONS of books and methodologies about how to be a Business Analyst, but in the end, you have to make the call. Evaluate the personalities of every member of your team. What are their motivations, their desires? Tailor your relationships to them accordingly. That's not to say you shouldn't study the wide variety of techniques offered by different methodologies, but a fully XP approach will not fit most developer's personality or approach to work. Most of all, try to set your team up for success. Learn to recognize their needs and use that as a tool to celebrate when tasks are completed. It's about results, not about how you get there, after all.