Effective public speakers are relaxed, well-practiced, descriptive and personable with their audience. They also tend to be well-prepared, often having rehearsed their speech using visualization techniques.
The best public speakers typically assign more value to effectiveness in communication than they do to perfection. In other words, when they make a mistake, their reaction will be to carry on with their speech regardless, prioritizing fluency, unless the mistake could impact people's comprehension.
The ability to structure thoughts and connect with the audience is also crucial to being an effective public speaker. For instance, speakers might connect with their audiences immediately by way of an attention-grabbing joke or anecdote, before outlining in a preview statement the points they intend to cover.