Rehearse your talk. Use as few words as possible. If you need to use too many words to explain some notion, your notion needs to be broken up and to be told as two or more. Poorly prepared speakers tend to use too many words. Strunk 's advice Omit needless words is relevant.
Vigorous writing is concise.
A sentence should contain no unnecessary words, a paragraph no unnecessary sentences, for the same reason that a drawing should have no unnecessary lines and a machine no unnecessary parts. This requires not that the writer make all his sentences short, or that he avoid all detail and treat his subjects only in outline, but that every word tell. Speak slowly and articulate. Try to determine whether the person sitting in the last row can hear you clearly. If you cannot explain your concept using few words spoken slowly, you will not be able to explain it using many words spoken rapidly.