The document provides instructions on how to write an effective paragraph. It states that a paragraph should present a single main idea, begin with a topic sentence introducing this idea, and include supporting sentences that provide details and maintain coherence. It emphasizes that a paragraph needs unity around one topic, coherence in its flow, an explicit topic sentence, and sufficient development to explain the main idea without leaving the reader with unanswered questions. Examples are given to illustrate these components of an effective paragraph.