We worry about the content, we tweak the structure, we spend hours on the slideshow, we lose sleep, and we may even make the time for practise. But we forget this: Most times when you do a presentation, you do it on your subject of expertise. So you need not worry about the content at all, you should simply decide what snippets to select and then structure in a manner that makes sense using an opening, body and conclusion. Then focus your attention of how you put the message across. Think about how you look, how you will appear to the audience and use your friend when you practice.