The key principles of writing effective essays for the UPSC exam include maintaining a clear structure, which comprises an introduction, body, and conclusion. It is essential to present a strong thesis statement that guides the narrative. Using relevant examples and illustrations enhances the argument, while a balanced view addressing multiple perspectives enriches the content. Employing clarity in language and avoiding jargon ensures comprehensibility. Time management is crucial, so practicing under timed conditions helps refine skills. Finally, thorough editing for grammar and coherence significantly improves the final output.