In her book, The Non-Designers Presentation Book, author Robin Williams argues that a presentation should start with an introduction into the topic, like the preface in a book.
[I]t's the foreplay before you start reading. We enjoy that process., she writes.
I happen to disagree with this advice. Actually, I've stopped reading forewords in books. They usually only tell me how important the topic is or how great the author is. I'm not interested in this any more. I already bought the book; just take me to the content already!