Practice natural gestures and use them to make your talk more interesting. Practice changing the speed at which you talk, emphasizing words by speaking at different cadences. Use pauses to help get points across. Don't forget the power of humor. Remember to eat something nutritious beforehand so that you are not hungry and your blood sugar is not low.
Good ideas are whole grain snacks, fresh fruit or decaffeinated tea.
From the beginning, your audience will begin forming opinions, before you even open your mouth. Most speakers dress in more businesslike attire than the audience, paying careful attention to their clothing, shoes, hosiery, jewelry, hairstyle and makeup. How you dress is easily controlled. Be sure your clothing allows you to breathe easily and your shoes are comfortable for standing for a while. Your facial expression is important.