To inform or describe: Know the audience's current level of knowledge – if jargon is necessary and they are unfamiliar with it, you must explain the meaning of the words. Use anecdotes, examples and illustrations to give life and colour. Use deductive, chronological or spatial order and carefully chosen words to describe things precisely.
describing observations, background against which something has happened, facts and details: Deductive approaches can involve presentations that can be built up layer by layer, and allow the audience to understand your reasoning. Another way of understanding how you reached your final conclusion would be to present events in a time-based series (chronological).
To instruct or explain: Concentrate on showing, either by means of diagrams, pictures or demonstrations. Your words must be chosen to produce clear visual images which the audience can grasp.
explanations, directions, instruction: Analogy can be helpful here. Describe something the audience is familiar with: ‘This process is rather like…’
you are concerned with explaining how things work, how processes or procedures are carried out, how actions are performed; you may also want to include an explanation of why things are the way they are and why certain steps are taken in a process: Usually deductive, chronological or spatial order is most suitable but if you are concentrating on why a procedure is necessary, or is the way it is, a less systematic ordering might be appropriate.
To persuade, convince or inspire: Recognise how difficult a task this is: you must appeal to the heart and the head by quoting audience benefits and evidence to back up your arguments – statistics, authoritative opinion, experience of others – but these must be accurate and relevant.
usually changing beliefs, attitudes or behaviour: Avoid generalising and exaggerating, ‘emotive’ and ‘coloured’ language. If you base your argument on assumptions, explain those assumptions.
presenting a case or an argument in favour of or against: Avoid, or at least admit, your prejudices. Give some reference to the other side of the story, or your case will be weakened.Above all,
(a) you must get the audience's attention,
(b) find out what the audience's needs and interests are,
(c) show how you can satisfy those needs,
(d) ask for an appropriate reaction or approval.
To entertain or amuse: More than any, this kind of speaking is an art to which some people seem born; however, since we may all have to do it sometime, it is worth learning.
vote of thanks, ‘after-dinner’ speech: The general guidelines are: be brief, ration the humour (quotations, i.e. other people's humour, can be very useful here); relate your speech to the audience's interests and to the occasion – be personal and particular.
Credit to : http://openlearn.open.ac.uk/
