Start your speech with a premise. In writing, this would be called a hypothesis or thesis statement. Ensure the conclusion logically flows from your premise and that all the contents of your speech support both your conclusion and premise.
Use ideas in your speech that you have a strong reason to believe are true. Make sure they are relevant to the speech and support your overall argument.
Don't make claims that you can't support with facts or theories discovered by credible research. Strong persuasive speeches don't communicate opinions that can't be supported by evidence.
Don`t speak with the intention to manipulate. Manipulation can occur by using tactics such as fear, which diverts the audience's attention from the main issue. For example, a persuasive speech about banning capital punishment might say, "Imagine if you were the one who was about to die."
Don't assume that everyone holds an opinion. For example, "Most people believe that capital punishment is unholy." This is also a fallacy because it assumes most people believe in the teachings of the Bible.