John Morley's updated book "Scriptwriting for High-Impact Videos".
Amazon sells it and the previous edition.
It really is a great guide to success in working a training or promo video project thru all the creative steps and making it have the best possible chance of success. Equally useful for writers and non-writing producers. If you ever saw a corporate media project, or made one, that just failed utterly, and you don't know why, or you know why but not how to get out of it, you need this book. It covers the main tactical and strategic errors made by beginners, it sets out very clear steps to walk you thru the creative treatment process, the heart of a good project. Get this part right, everything else becomes a relative cakewalk. Very fast read, but you will refer back to it over and over.
No, John is not paying me for my endorsement, but I've been making a living in video from the ideas in his book, ever since the first edition came out, so in a way, he's already paid me. :-)