Choose a topic that you care deeply about when you are learning how to write persuasive speeches. Select something that you have a strong opinion on and don't mind doing a lot of research on. Think about a political issue, moral issue or social issue that interests you and develop a thesis statement about it. Write your thesis statement in one succinct statement such as "Tax increases are counterproductive to economic growth" or "The government should ban nuclear weapons."
Research your topic thoroughly and develop four points that support your thesis statement. Think about what convinced you of the opinion you hold. Create two points supported by factual evidence that something is wrong, is harmful or is a problem. Follow that with two points about how to solve the problem or right the wrong that you have raised. Include statistics, court cases, expert opinions, personal experience or the experiences of others to strengthen your points.
Write an introduction that grabs your audience's attention. Write a dramatic opening statement. State your thesis and preview your four points. Write a conclusion that sums up your argument and restates the critical danger of not taking any action or not changing one's mind about the topic or opinion you just argued.
Practice delivering your speech often before you have to give it. Write key points and evidence on note cards to refer to, but not read from, when delivering your speech.