The spoken word differs from the written. Audiences for public speeches do not have the benefit of being able to go back and re-read sentences. They cannot look at a page and see section headings or new paragraph indentations. Public audiences have a more limited capacity to comprehend complicated ideas and to take in long sentences and difficult or dense language. Public speakers have to compensate for these limits by using the principles of repetition of content, clarity of structure, and simplicity of language.
Repetition
Repetition is a fundamental part of most good public speeches. An old public speaking adage goes something like: “tell ‘em what you’re going to tell ‘em, tell ‘em, and then tell ‘em what you told ‘em.” By the end of a speech, an audience should have absolutely no question about what the central idea or main claim is.
To make sure that happens, state that idea clearly in the introduction of your speech, tie the information and arguments of the body to it in explicit ways, and restate the idea again in your conclusion. Audiences are more likely to miss or forget important information if you do not repeat and restate it.
Clarity
Clarity of structure means that ideas are logically grouped into categories the audience can easily understand. In addition, just as paragraph indents and underlining alert readers to new or important ideas, transitions and signposts help listeners recognize new 'paragraphs' and key points of the speech.
Brief pauses can signal to listeners that the speaker is about to say something important or is moving onto the next main point. Phrases like "most important," "I am claiming that," "the crucial point is this," call your listeners' attention to what follows them and act as verbal underlining.
Simplicity
Simplicity in language is crucial to conveying information effectively. Oral discourse differs from written in its use of language. Oral discourse is often best when it uses the first person, “I” and “we.” Such language gives the speech a sense of immediacy and helps the speaker to connect with the audience.
In addition, good speeches will often use less formal language--contractions, sentence fragments, selected slang expressions. Finally, oral language needs to be less dense and jargon-laden then some kinds of written language, especially academic language. When written papers are read out loud, they almost never make effective speeches.
While there are several effective modes of delivery, extemporaneous speaking is the most adaptable and time efficient. Learning it is also an excellent way of sharpening critical thinking. Extemporaneous speeches are developed through outlining ideas, not writing them out word-for-word. They are practiced ahead of time, rehearsed and re-rehearsed (extemporaneous speeches are not impromptu), using a keyword outline of single words and short, 3-5 word phrases.
The speech is not memorized but instead is concentrating on the main ideas; each time a speaker practices and delivers the speech, wording comes out a little differently. Extemporaneous delivery gives the speech freshness, for it doesn't sound canned and over-rehearsed. Additionally, this flexible form of delivery allows a speaker to make adjustments to their speech in response to non-verbal signals from the audience--signs of confusion, displeasure, curiosity, or excitement.
Extemporaneous delivery allows speakers to make eye contact with the audience—one of the best ways to connect with them and keep them involved in the speech. Eye contact is an important way to establish a speaker's credibility and make a speech compelling; when a speaker relies too much on notes, they are potentially losing their audience and running the risk of looking unprepared.
Verbal and nonverbal communication is important in public speaking, helping to make a speech clear and compelling to an audience. Developing good vocal delivery means focusing first and foremost on being heard clearly: a speaker must speak loudly enough to be heard by everyone, articulate words sharply so they can be understood, and speak slowly enough so that the audience can easily take in the ideas.
In addition, avoid monotone delivery and be engaged enough with the speech to communicate interest. Effective bodily delivery begins with this simple maxim: do not distract the audience with extraneous movement. Nervous pacing, standing cross-armed or hands-in-pockets for long stretches, turning from the audience and talking into a visual aid, gestures unrelated to the verbal message--all of these distract from the content of the speech and should be avoided.