Establish a position or proposition about a debatable issue. Some topics are fact-based and not debatable. According to Diana Hacker, whose book "Rules For Writers" provides essay and research guidance for college writers, debatable topics are those on which reasonable and informed people might disagree.
Consider the audience. Hacker points out that the aim of an argumentative essay is to provide new reasons for readers to reconsider their position on an issue. The development of the argument depends on readers' knowledge and opinions about the subject. Classical argumentation offers three ways to appeal to an audience: through logos (appeals to logic and reason), ethos (appeals to morals and ethics), and pathos (appeals to emotion).
Write an introduction that includes a lead-in that captures readers' attention and presents your topic. Include a clear statement of the issue and your position on it: the thesis. Provide a brief but complete summary of background information that establishes the context and relevance of the issue and its connection to your thesis.
Compose a series of body paragraphs, each of which presents one point of your argument. Include factual and objective supporting material for each point. Include documented source materials such as examples, statistics, quotations from experts and research data whenever possible. Provide attribution and references for all outside sources.
Acknowledge counter arguments and opposing viewpoints fairly and accurately. Concede the validity of at least some aspects of the opposing viewpoint to create rapport with potentially hostile readers and establish your credibility as a reasoned, balanced writer.
Rebut or minimize these counter arguments using documented evidence that supports your position. This material can appear anywhere in the essay. Place a paragraph establishing the strongest counter arguments just before the argument, or raise and challenge a particular aspect of the opposing view in each of the supporting paragraphs.
Close the argumentative essay with a conclusion that reinforces the most important points of your argument. Review the introduction for points to revisit. Echo the key ideas from the background or reestablish common ground with the audience to bring the essay full circle and create a sense of closure.
Provide references for the supporting evidence. Include a detailed list of works consulted in research and cited in the text to bolster credibility and strengthen your argument. Consult discipline-appropriate writers' guides such as the "MLA Handbook for Writers of Research Papers" for formatting conventions.