Picking, refining, Examples in general.
Examples are a tricky subject. Everyone has their own examples because Impromptu speaking is all about what you're comfortable talking about. People have all sorts of methods to pick examples, because it's the easiest part of impromptu to prepare and codify. I don't like the interpretation that if you just have a million examples you'll win. Like I said, this is only the third most important aspect of impromptu. If you've got a solid interpretation and are looking for a main example, you'll do well even if your entire speech is about Alexander the Great during the Battle of Guagamela.
I tend toward business and history examples and definitely away from pop culture examples, just because it's easy for me to put my interpretations in terms of past events or modern methods of dealing with common problems. And I don't watch a lot of movies or TV, so my pop culture is limited. I do use House, M.D. a lot. Favorite TV show ^_^
Here's how you come up with good examples: Pick three or four general topics, such as History, Theories, Pop Culture, and Literature. This is just so you're guaranteed variety in your examples: three historical examples are boring. Mix it up unless your audience is full of history majors. Even then, they'll appreciate the variety.
I group people in with their main group. For example, my constant Alexander the Great examples fit under History, Steve Jobs goes under Pop Culture (as does all history from the last 20 years), Faust is in Literature, and Thomas Hobbes is in Theories. There are some people who cross fields. One of the reasons I like using Machiavelli and Google are because of this fact: Machiavelli's the Prince works for Literature, has theories in it, and the guy himself has an interesting history. Google is a business/Pop Culture example, a good story (it'll fit in history when it's not pop culture anymore), and their motto and purpose statements show unique theories.
Here's how I sort and record my examples:
History examples: First, make an in-depth timeline. Then note major people involved with each event, then note major cultural clashes or battles. Again, major people on each side of the conflict are useful to give your audience something to latch on to. When using history examples, begin with a brief summary of the times, then mention the important people, before finally stating why it's relevant in the terms of the quotation.
Example (Shortened version of my entry for Rome):
Founding- circa 9th century BC (753?)
Romulus/Remus found city. Romulus kills his brother and gives city his own name.
Rule of the Seven Kings of Rome- 753-509
Final king of Rome thrown out by ancestor of Brutus.
Creation of the Republic- 509 BC
Rome takes advantage of pressed Etruscans to rebel and form a republic with other latin city-states.
Gauls invade Rome- 390 BC
Rome Rebuilds city quickly and goes on the offensive, securing northern marches and continuing in conquest until Punic Wars, at which time Rome is foremost city on the Italian peninsula.
Punic Wars- 264-146 BC
Rome V. Carthage for dominance of Mediterranean. Roman Statesman Cato ends every speech with ‘Destroy Carthage,’ no matter the topic. In 146, Carthage and Corinth are razed.
Social and Civil wars, emergence of Marius, Sulla, Pompey, Caesar- 146-44BC
At the time, Rome dominates Mediterranean, largest city in the world until 19th century. Size maintained by subsidies, not trade like Alexandria.
Roman Empire- possibly at Julius Caesar’s claiming of dictatorship(44), battle of Actium (31), or date of granting of Augustus title to Octavian (27).
Roman republic had been weakened by the Gaius Marius v. Sulla, followed by the civil war of Julius Caesar v. Pompey. Caesar wins, takes title of Dictator Perpetuus. Caesar is assassinated by senators fearful that he would take the title of monarch, led by Brutus. War follows between his heir, Octavian, and Marc Antony. Octavian wins and is crowned Augustus, gains no more technical power, but is in essence dictator behind the scenes of the republic.
Romulus/Remus, Kings of Rome, Brutii family, Cato, Gaius Marius, Sulla, Pompey, Julius Caesar, Marc Antony, Augustus Caesar.
Founding, Creation of Republic, Gaul Invasion, Punic Wars, Civil Wars, battle of Actium, Creation of Empire.
Roman v. Carthaginian, Barbarian v. Roman, Hellenic V. Roman v. other
Back to Greed is Good. Say my main example is Julius Caesar. I'd start out with
'About 50 years before the birth of Christ, Rome was in the middle of a huge civil war. On one side were Julius Caesar and his forces, and against them were the armies of Pompey. Of course, we all know Julius Caesar won, and the reason why he won was because he was greedy for a new Rome. His greed for what was, essentially, a dictatorship in the place of the republic which had brought about the civil war drove him to ignore his rationality and defeat the forces of Pompey. However, once he had won the war, he spared many of Pompey's generals because he knew that they were just greedy like he was; they were hungry for a better Rome. Julius Caesar's greed in wanting to personally remake all of Rome first drove him to irrationally fight a civil war and then let him empathize with the same attribute in his former enemies and grant them leniency. But it was this same series of events which would later lead to his death in the Senate at the hands of those people he spared. So we wonder... How good for Caesar was his greed? This leads us into today's quotation..."
43 seconds. Too long for an intro unless you've prepped for under 30 seconds, but it's typed out. I'm much more verbose in print. ^_^ and I love my long intros.
That should give you an example of how to use examples. I suggest doing single example preps, where you get a quotation, form your argument, and try out whatever new example you've got as the main example. It will give you a good idea of how useful your example is and how to phrase it in a speech.
Remember, just like any other activity, public speaking requires constant practice. However, it is much easier to practice impromptu and extemp than other events; just talk to people. Try using an impromptu example in normal conversation, a pop culture one if you like. Whip out a 'Well, Google's corporate motto is 'Do no evil.' They've made it work, why can't we?' at your job, or a historical example in the middle of class to illustrate a point. It seems weird, but I guarantee it'll at least give you something else to talk about.