I believe that when it comes to preparing any kind of talk, you’ll make the best use of your time by applying this simple method: take whatever time you have to create your masterpiece, and divide it in two. You could have allowed yourself 5 hours or 5 minutes, it doesn’t matter. What’s vital is that you use the first half of your time to write the piece, and the second half to rehearse it. Here are two scenarios:
The stupid mistake people make with a presentation with slides is to think that the slides are all that matter, that the material will speak for itself and not require any effort on the part of the speaker. Which is a bit like thinking that buying great ingredients makes you a great chef.
Write down your ideas, get them into a solid structure and remove the unnecessary material (see my post ‘Presentation Fails and How to Fix Them #7: Structure‘).
Aim to stop working on your text/cues/slides by the two-and-a-half hour mark. And when you hit that crucial point, STOP messing about with the material. Step away from the keyboard/notepad and start saying the words out loud. Get used to the flow of the piece, and don’t change the material, UNLESS you’re removing something, in which case you have my permission. Changing the order is also OK if you feel really strongly about it but try to minimise last-minute faffing about.
Write down the main idea, with a word or two giving some kind of verbal illustration of why it’s so important. Then run through it (and I appreciate that this may have to be in your head) to get used to the material, but for goodness’ sake don’t edit it at this stage or you’ll confuse yourself.
Using this approach means that you incorporate a good amount of rehearsal. Looking surprised at the content of one of your slides doesn’t fill your audience with confidence, but referring to something which then appears on a slide makes you look in control, which really does fill an audience with confidence. You can, of course, start rehearsing immediately. This means writing by saying the words out loud, in which case you should still stop changing the material when you reach the halfway mark.