In a recent article on Rules for Public Speaking the President of the City Club of San Diego, George Mitrovich, started off by giving some excellent advice on what NOT to do at the beginning of a speech:
“Whenever a speaker begins his or her remarks by saying, ‘I'm not a public speaker’, my friend and I will, at that point, get up and leave. Why? If you think you're not a public speaker then why speak? Why trouble your audience? Why waste their time? There's already sufficient boredom in this life, why add to it?”
So, please don’t begin by shooting yourself in the foot! Also, don’t tell the audience that you’re really, really nervous about speaking. They usually can’t tell that, unless you blurt it out.