Feel confident about your presentation. When you give your class a presentation, your teacher is essentially having you take over their job for a little while. It's your job to make sure everyone understands what you're trying to tell them. Make sure you pay attention to how your teacher does this before your presentation, because teachers are expert presenters.
Visualize success before, during, and after your presentation. Be humble about what you do — no need for cockiness — but imagine a successful presentation at all times. Don't let the thought of failure creep into your mind.
In many ways, your confidence is just as important as the information you're delivering. You don't want to spread misinformation, or skimp on doing your research, but a lot of what you'll be graded on — and what the other students come away with — is going to be your level of confidence. Also if you are confident, you will have a better time exchanging ideas with the class.
If you need a confidence boost, think big picture. After 10 or 15 minutes, your presentation will be over. What will your presentation matter in the long run? Probably not very much. Try to do the best you can, but if you're getting nervous, remind yourself that there are much more important moments in your life to come.