I'd start by locating colleges that offer either a degree or certification in Public Speaking/Consulting. As for gaining experience and further more, skill, you have to simply get out and do some actual public speaking. I once heard of a guy who wanted to get into this sort of thing but he had problems speaking in front of large amounts of people and/or higher-ups. He decided to go out in the middle of his town square and stand on a milk crate whilst he spoke about public speaking.
One thing that has helped me build social/public skills in general over the years is watching speeches. Pick up on key movements and transitions. A lot of times you pick up most of that stuff passively. Good luck.