You might try Toastmasters. Once you get past the first few "nervousness" lessons they focus on how to convey meaning with speech. Every chapter is different, so YMMV. Several of the speeches you have to prepare cover persuasion, motivation, and how to structure a speech so that everyone remembers exactly what you want them to remember. They teach through having you give a series of 5-7 minute speeches, but I've found the practice helpful beyond giving a formal talk.
I second Toastmasters. They took me from a shy undergraduate who had panic attacks the night before speaking in front of a class and turned me into someone who genuinely loves public speaking and hasn't used notes to speak in over a decade!!
There are two caveats to Toastmasters:
- each chapter is different. I have now belonged to three and loved two. The third chapter was my personal hell of realtors and financial managers who were trolling for clients. My self promotion allergy was way too active...
- you get exactly what you put into TM. I know a guy who started in the same chapter at the same time as me. I spoke every chance that I could get and improved quickly. He was never willing to truly embarrass himself, rarely spoke and got next to nothing out of the organization.
