Writing the Introduction
The role of an introduction in a cause-and-effect essay is twofold. First, it must describe the background of the issue, explaining what the cause being discussed is and why it is important to understand its effects. Alternatively, the essay may be analyzing the causes of a known effect. In either case, the purpose of the introduction is to explain the issues at stake and to concisely state the purpose of the essay. A thesis statement -- a brief statement of the essay's argument -- should be the conclusion of this paragraph.
Body Paragraph Structure
A typical five-paragraph essay has three body paragraphs. Each body paragraph presents a piece of evidence as part of the essay's overall argument. The exact division of the paragraphs depends on the student's approach to the essay; for example, an essay that is asked to explain the effects of a particular cause will probably spend one paragraph describing the cause and two paragraphs explaining its effects, while an essay asked to analyze the causes of a particular effect will reverse this structure.
Body Paragraph Content
Although each essay will have different body paragraphs depending on the points the writer intends to make, all body paragraphs will have certain similarities. Each paragraph should describe a single feature of the essay's argument -- a particular cause of an effect or a particular effect of a cause. The first sentence in the paragraph, in combination with the last sentence of the previous one, should provide a clear transition. The heart of the paragraph will be a clear description and analysis of the relationship between cause and effect.
Writing the Conclusion
The conclusion of an essay, being the last thing the reader encounters, is one of the most important parts and the most likely to leave a lasting impression. The conclusion draws together the evidence presented in the body paragraphs, summarizes them and presents the writer's analysis of the question. The final sentence of this paragraph, while not exactly the same as the final sentence of the introduction, should restate the essay's main point, now supported by the evidence of the body paragraphs.