Last week I gave a presentation to a large group of people who work for Fremantle, one of the largest international TV production companies in the world. It went OK but could have gone better, and the reason was that I forgot the oldest rule in the book for presentations (which also applies to articles and non-fiction books):
tell them what you're going to tell them, tell them, then tell them what you told them.
My talk was a slightly eccentric look at creativity and how we can be more creative intentionally rather than waiting for inspiration. I assumed that the audience would see how it all fit together, but I think some of them didn't--my fault, not theirs.
The following day I presented a workshop and was careful to specify exactly the purpose of each of the 3 exercises, and that went much better.
It's frustrating to still make basic mistakes when I've been doing this kind of stuff for quite a while. But then another mistake is to expect not to make mistakes...