Whenever anyone wishes to persuade anyone else of something, he is engaging in a kind of oratory. One example of great oratory includes Abraham Lincoln's Gettysburg Address. In this famous speech, Lincoln argues in favor of the principles of liberty and pays homage to the sacrifice of the fallen. Another example of oratory is Martin Luther King's I Have a Dream speech, in which King argues in favor of racial equality and ending racial discrimination.
Choose a topic that you're already passionate about or familiar with. Body language is important in giving speeches and if you're already excited about the topic, this will show in your mannerism and gestures. Pick a topic that can be easily researched, as you'll want to back up your arguments with facts and statistics. Anticipate questions and be sure to know about hot-button issues connected with your topic. If you're assigned a topic, be sure to familiarize yourself with the issue extensively before taking your speech to an audience.
Over the centuries, orators have developed a basic structure or outline for speeches that can be used for speeches of any topic. This structure consists of an introduction, identification of the problem, identification of the cause of the problem, discussion of the effects of the problem, arguing for a particular solution to a problem and a conclusion.
There are three basic techniques for persuading people. These techniques are called "modes" of persuasion. The three modes of persuasion are ethos, logos and pathos. Ethos refers to persuasion based on the character of the orator. If the orator refers to herself as an "honest woman" or a "simple woman" she is using ethos. Logos refers to logical arguments and evidence. If an orator refers to facts or statistics then he is using logos. Pathos refers to emotional appeals. Each of these modes can be used with many speech topics.