One of the first traps that I have difficulties getting out of (it still happens sometimes), is the slides-first approach.
Though it might seem really effective to start with the introduction slide (“Hey look, slide nr. 1 is done!”) it might cause the presentation to become much less effective – and in many cases it will take you even more time to create the presentation if you start off this way. In some of my best presentations, creating the slides took me less than 25% of the preparation time.
My (ideal) approach: I would first think about what the main message I want to convey in the presentation. Once I know what the point (I call it “one core message”) of the presentation is, I start to create a story and some supporting arguments to develop the presentation.
By “story” I don’t mean you have to talk about tales and drama (though you could, if you wanted to!), but I am talking about a storyline which is easy to follow. One simple way is to start with a problem, then talking about the challenges of the problem and then talking about the solution (An example: “You know how boring presentations can be? People don’t pay attention. But at the same time it’s really hard to improve presentation skills. Well, here’s the solution” and so on or “Last year we had bad sales. This made us have to cut a few corners this year and go some rough times. Here’s how we can turn this around.”). But there are many other examples on how to create storylines.
If you want, you can create a storyboard (a broad overview of how the slides are going to be structured and how they are going to look like). And only once I’m done with all that do I start with the slides. In some cases, I can almost turn off my head, because I already have a good idea of how the slides are going to look like.