In the opening sentence, make your point. This is also known as the topic sentence.
A. Topic Selection -- What is it you will argue for? What makes you angry, sad, empathetic? What are current problems in society I would like to see changed?
B. Claim Selection -- What is the claim you wish to argue/present?
C. Narrowing Your Purpose -- While the general purpose is to persuade, narrow it more specifically in light of what your listeners already know and do, how they feel, and what they value.
Information summarized from Chapter 17 of Clella Jaffe's Public Speaking: Concepts and Skills for a Diverse Society. 5th ed. Belmont, CA: Thomas Wadsworth, 2007. Print.