Essential skills for success in the UPSC civil services interview include communication, critical thinking, and the ability to express ideas clearly and confidently. Candidates should be adept at articulating their perspective on various issues while demonstrating a sound understanding of current affairs and socio-economic contexts. Additionally, effective interpersonal skills are crucial, as aspirants must engage with a diverse panel of interviewers. Analytical thinking and the ability to remain composed under pressure are also important, enhancing the candidate's overall performance and impression during the interview.