For one, breathe. Before, during, after. Breathe. Settle yourself (I meditate daily as well). Personally, I think I get caught up when I try to read word for word scripts, so I always give myself a general blueprint of what I want to say but allow myself room for improv. I also tend to do my practice speeches way faster than the real ones, which I also think is the opposite of what most people experience. I pause a lot (and, again, breathe) during speeches, let things sink in for both the audience and myself. That's about it. Oh, I try to get everyone laughing early on. It settles the nerves in almost any situation.