Studies at the University of California examined the impact on an audience of the words a presenter speaks, his or her tone of voice, and body language. Surprisingly, it turns out that your words–the message you want to convey–amount to only 7% of the impact you make. Tone of voice accounts for 38% and body language generates 55%, well over half of the impact.
That means you need to do all you can to use tone of voice and body language to support your message (words), rather than detract from it. If you look up tight and locked down as you present, your audience will be up tight about your message. If you speak in a tone that is consistently sarcastic or meek or hesitant, for instance, your audience may tend to view your message with sarcasm, meekness or hesitancy.
Practice using gestures to animate your body language, your facial expression and your vocal pace and pitch. It may feel stilted at first, but eventually you’ll be able to incorporate gestures very naturally, just as you do in casual conversation with friends. Increase your emphasis on key words and phrases when you speak to overcome a monotonous delivery, and use pauses for emphasis, as well. If you speak at about 150 words per minute, increased emphasis and occasional pauses will sound natural and can be used effectively .