These may be presentation ideas for kids, high school students, for teachers or for interviews. However, the topic you choose must be relevant to audience. A relevant topic is the one, which the audience relates to.
Make your presentation as crisp and clear as possible. As an advice for school projects, don't complicate things, by adding inscrutable and pedantic jargon. This will baffle both you and the target audience.
Just as we get bored while listening to an unending speech, a long presentation from your side is also going to get boring. Keep it short and simple. People will understand it better and comprehend it even better.
Rehearse your presentation till it's perfected, before the D-day. To make your presentation effective, by heart couple of last lines and make an eye contact with the audience. This will show your conviction and confidence.