INTRODUCTION. Remember that this is an extremely diverse group and that many of the people may not understand the subtle aspects of your area very well (and in fact may not have any idea at first what you're talking about). Spend a couple of minutes on a careful, clear and well-thought-out introduction to explain exactly what you've been doing or are planning to do, why you're doing it (e.g., a question that's arisen from previous work), and why it's important. A very common mistake has been to take so much time for the introduction that there's not enough for the rest of the talk.