Best practices for writing effective essays in the UPSC Mains involve focusing on clarity, coherence, and relevance. Structuring essays with a clear introduction, body, and conclusion allows for logical flow, enhancing readability. Candidates should engage in extensive reading to gather diverse perspectives and insights on pertinent topics. Effective use of examples, personal experiences, and current affairs enriches the content. Additionally, practicing time management during essay writing helps candidates express thoughts within the allotted time, subsequently leading to well-rounded, impactful essays.