Who are they? What side of the issue are they likely to be on? Are you preaching to the choir or is the audience divided? What will convince them to hear you out? Are they sympathetic and trusting or skeptical and full of questions? What does the audience already know about the issue? Are they experts in the field or new to the topic? How much information will they need? What kind of evidence does your audience trust? Do you want to leave them with food for thought or a call to action? In the end, of what do you want to convince them?