You are free to organize and develop your response in any way you think will enable you to effectively communicate your ideas about the issue. Your response may incorporate particular writing strategies learned in English composition or writing-intensive college courses. GRE® raters will not be looking for a particular developmental strategy or mode of writing; in fact, when GRE raters are trained, they review hundreds of Issue responses that, although highly diverse in content and form, display similar levels of critical thinking and persuasive writing.
Raters will see some Issue responses at the 6 score level that begin by briefly summarizing the writer's position on the issue and then explicitly announcing the main points to be argued. They will see others that lead into the writer's position by making a prediction, asking a series of questions, describing a scenario or defining critical terms in the quotation. The raters know that a writer can earn a high score by giving multiple examples or by presenting a single, extended example. Look at the sample Issue responses, particularly those at the 5 and 6 score levels, to see how other writers have successfully developed and organized their arguments.
You should use as many or as few paragraphs as you consider appropriate for your argument; e.g., you will probably need to create a new paragraph whenever your discussion shifts to a new cluster of ideas. What matters is not the number of examples, the number of paragraphs or the form your argument takes, but the cogency of your ideas about the issue and the clarity and skill with which you communicate those ideas to academic raters.