Persuasive public speaking is not only reserved for politicians and sales people, nor should it be. On some level we all have a message we want to communicate which we know will be of great help to others.
In order for others to benefit from your message they must first buy into it.
In order for that to happen you must be able to influence them. That's what persuasion is all about.
Even when you have something a person needs, it requires persuasion to help them see it in a way that makes sense to them. Too many times people don't realize how they can be helped by others. And the gap here has only to do with the information not being conveyed in a way that allows them to understand the benefit to them.
There are two legs which must be understood when formulating the persuasive speech.
The first is the basic framework of persuasion,
The second is the subject matter of the speech.
Both components are relatively simple. When you blend them in a balanced way, you effectively build yourself a formidable presentation.
The basic framework for persuasive public speaking consists of three elements: Isolate the concern(s), identify the source(s), produce practical solutions.
An example of this framework would look like this:
First, isolate the concern and make it managable. World hunger is too big a scope to speak to. However, providing lunch for the children in your local elementary school is something people can feel they're capable of helping with.
Second, Identify the source of the concern. People have an insatiable desire to assign blame - whether it be to another person, or a natural cause, or circumstance. Your position is to identify it clearly, and logically connect it to the concern, then stand up for it with sensitivity and passion.
After you've clearly presented the concern, and persuaded the audience of its source, you must produce solutions that can be implemented here and now. You must have available to your audience, right then and there, some way for them to take action.
When it comes to the subject matter of the persuasive speech, four elements have to be present: You must appeal to both the head and the heart (offer both facts as well as emotional appeal), you must be credible, and your audience must believe that you are one with them; that the connection is real.
That's the essence of persuasive public speaking in a nutshell.