Essential skills for effective communication during the UPSC interview include strong articulation, active listening, and the ability to think critically. Candidates should develop a clear and concise manner of expression while ensuring they remain engaged in the conversation. Non-verbal communication, such as maintaining eye contact and appropriate body language, plays a significant role in conveying confidence. Additionally, demonstrating knowledge of current affairs and an understanding of social issues is vital. Overall, these skills can significantly enhance communication and impression during the interview.