Begin by clearly defining rhetoric and applying that definition to the way your students will use it. This will vary depending on the age and abilities of your students. It might be a way of writing more effective essays, or a means for analyzing and explaining political debate or classical literature.
Analyze arguments on a particular topic, ideally those giving different viewpoints, so students can compare how different points of view have been presented. Make sure they have incomplete or ineffective arguments to study as well as effective ones, so they can learn to recognize the difference.
Break this analysis down and discuss the different ways writers have used to convey their arguments, how they have structured their work and why they think that approach was taken.
Identify three aspects of the work: the argument being presented, the message that the author is trying to convey and the audience at which the work is aimed. Discuss how the message will change depending on the intended audience and how this can add to the effectiveness of the argument.
Instruct students to create their own argument on a chosen topic. Tell them to present a clear opinion on that topic and to back it up with clear evidence supporting their view. Try to have students present different views on each topic, so the merits and persuasiveness of various arguments can be compared. The emphasis should not be on an argument being "wrong" or "right" but on the quality of the presentation of that argument.
Ask some students to present their arguments to the group in speech form. Use this to illustrate and teach how different techniques can be effective when using the spoken word, compared to a written argument.