How do I slow down my speech?

People tend to speak very fast for a few different reasons, but the main reason is nervousness. If you are nervous, your brain is working rapidly, your heart is beating fast, and you are going to speak so quickly. Pause and allow there to be a little silence. In that pause, think about the next thing you're going to say. So think before you speak, not at the same time when you are speaking. If you can make yourself stop and format what you want to say, that lowers your heart rate, calms you down, and makes you a little bit more clear.