Some presentations fail to impress because key elements are missing. Many more fail because they contain too much information. Information overload is ever present in our modern society. The presentation that impresses with a powerful message is the one that is sharp and focused on its aim. So, how to make sure that your presentation doesn't fall into the trap of giving your audience more information just because you can.
Question: What is it precisely that you want your audience to understand - not just know - at the end of your presentation? Can you explain this aim in one sentence? If you can, write it down. If you can't then work at it until you can. If it won't fit into one sensible sentence then you have more than one aim and need more than one presentation.
Keep this aim in mind throughout the planning phase. Build out from the aim, use mind-mapping or other planning aids if you are comfortable with them. Immediately around the aim are clustered facts and figures that are essential. Further out there is supporting information that is important. As you get further away the importance and the relevance drops off sharply. Be ruthless and eliminate everything that doesn't build a picture of your aim in the mind of your audience.
Note down all the information, illustrations and arguments; whatever you need. If you are not sure in the early stages whether you need a particular item, leave it in. But have the courage to throw it out later if it is not needed. One check question is, 'would my audience feel cheated if they found out about this later?' If so, leave it in. You are not hiding things from your audience; just doing them the courtesy of their having to listen to only what is necessary.
Do not fall into the trap of filling a thirty minute slot (or whatever) just because you have been given that time. If you need less, say so. You will probably be thanked, especially if there is a busy programme. Of course, if you need more, ask. Never, ever, over-run your time. Few of us are good enough speakers for our audiences to want more than they asked for.
Do you know the difference between: an example and an anecdote; humour and jokes; friendliness and obsequiousness? For our purposes, the difference is what you leave in and what you discard. Do use examples if required; do not ramble off into irrelevant tales. Do be mildly humorous if appropriate; do not tell jokes, especially smutty ones. Do be as open and friendly as the occasion allows; do not attempt to suck up to your audience.
If you stick to these rules, your presentation will be lean and sharp. The lines you draw from your arguments to your final conclusions will be clear. Your audience will understand exactly what you wanted them to understand without any distracting thoughts. Your chances of achieving you aim will be much higher. And if occasionally you do fail, at least you will know it was because you failed to convince them, not because you lost them on the way.