Rehearse your speech in front of friends or family who will be honest with you. Practicing in this manner helps you learn your speech, as well as providing useful feedback to improve your performance. Incorporate their advice into your speech and keep practicing, until everything is right.
Prepare an outline of the speech. While you should have the entire speech memorized, having an outline in front of you will give you confidence that you can continue, even if you forget something.
Dress as if you have something important to say. If you show up to give your speech in tattered jeans and an oversized T-shirt, you have sent the message that what you have to say is unimportant. You do not need to wear a suit, but a collared shirt and a pair of slacks, or a dress, send the message that you care about your topic.
Stand up straight and speak clearly. Your posture conveys your conviction about your message, and you want those in the back row to hear you clearly.
Provide an introduction that captivates the audience. Give them a fact or anecdote that prepares them to hear the rest of your speech.
Cover the topic in the same order as your outline, and with the same style you practiced many times in front of your friends. Conclude the speech with a final interesting piece of information that might inspire your audience to do more research on their own.