It might seem obvious, but preparation is one of the most underrated methods for ensuring an effective speech or presentation.
What does preparation look like?
If possible, build your own deck or write your own speech. When you practice, do it out loud. Videotape yourself practicing, identifying areas for improvement and take note of physical responses you may not be aware of. Anticipate what questions you may receive from your audience and think through how you will answer.
You can never prepare too much.