I've mentioned this book before, but it really deserves to be reviewed in more detail.
This was an invaluable resource to me at uni (and afterwards) while I was learning to lead Bible studies for the first time. It teaches you how to write studies from scratch yourself. Even though there are some really good study guides out there, this book will give you the confidence that you can read and understand the Bible yourself, and then teach it to others. The Bible is not a mystical kind of book that needs to be explained by gurus.
The authors, Karen Morris and Rod Morris, have extensive experience in adult education. Quite a few chapters are dedicated to explaining different learning styles (i.e. visual, auditory, kinaesthetic). I personally found Chapter 3: Learning from the Bible in groups to be the most helpful as it shows you how to apply the different learning styles to particular Bible passages. Some people find the question and answer method of Bible study quite boring so this chapter shows you how to use flow charts, diagrams, compare and contrast lists, role plays and drawings to assist people to learn effectively.
The book is quite a nice balance between teaching the mechanics of how to prepare a Bible study with the practicalities of leading a group and the issues Christian leaders need to wrestle with such as godly character and how to resolve conflict. There is also a chapter called Developing group life which shows you how to make sure your group is more than an academic exercise, but people who love each other dearly and seek to spur each other on in living for Christ.
If you're a Bible study leader, this is a must-have book. If you've ever considered leading a Bible study, but not sure if you're cut out for it, it may well give you some confidence to pursue this.