Types of Supporting Evidence
Facts are something that is known or can be proven to be true. Because facts can be proven, they provide powerful evidence for a speaker. Facts are useful to establish credibility.
Supporting evidence gathered from known experts carries a great deal of credibility. Remember that the people cited should be perceived as experts by others in the same field of expertise. Thus the author of a self-help book on psychology that has been rejected by professional psychologists would not be a considered an expert source. Also make sure the expert is talking about a topic in their area of expertise; an expert physicist is not necessarily an expert on psychological matters. Your testimony should also come from unbiased, third party sources. For example, the maker of a particular drug may not be an unbiased source on the attributes of that drug.
Examples are useful to illustrate your topic or to clarify complex issues.
Stories or Anecdotes
Personal experiences, your or others, lend a real life touch to a topic. When using personal experience consider whether or not the experience is consistent with other supporting evidence such as fact and expert opinion. Make sure the story you choose is appropriate to the point you would like to make.
A thoughtful quotation can be a good way to begin a speech; it can explain the topic or provide a memorable picture. Quotations can also be used as evidence if your quotation comes from an expert on the topic.