Some time ago I downloaded a mini public speaking guide by Simon Sinek, author of Start With Why.
Among the various tips, I found that one in particular was very useful and interesting. It's the idea of starting with the end in mind. If you begin to prepare a presentation having already in mind how you want to conclude, then every story you tell, every message and every idea will help you reach that conclusion.
The best way to prepare a presentation is to plan it in reverse. Instead of starting from the beginning (first I say this, then I say that, etc.) you should start from the end. Start with your final message – the idea that sums up your presentation – and then go back and think about what you have to say at the beginning and during your presentation in order to get to your conclusion.
Simon Sinek says that presenting is a bit like driving – you don't normally drive for hours without knowing where to go. Likewise, you can't begin preparing a presentation without knowing where to go. You can't begin preparing a presentation without knowing where you want your audience to go as a result of your message.