Concentration; But how much?
After a few sessions of public speaking, you would have already overcome your fear of speaking by then, hopefully. If you are thinking you have achieved the level of an expert in the world of public speaking, please don't. That's the time where your speech will waffle.
You repeat everything you have memorized the previous nights, though the flow of speech is there, but one thing you are desperately lacking in your speech : FORCE. A half-done work is no better than undone work. If somebody asks you a simple aritmethic equation, you wouldn't have given much thought to it, and you could easily answer him/her right?
i'm sure you are well aware of a science experiment , where you place a piece of paper under direct sunglight through a magnifying glass, and you start to move the magnifying glass slightly to focus the light beam onto the paper. What happen then? The paper starts to get burnt. Such is the power of concentration, if you divide your attention, your will power will be diminished.
Concentrate your every thought, word and feeling in your speech, and they will 'kick-off' ith force and every word you utter would have life& force on its own impacting the mind of the listeners.