Eligibility criteria for appearing in the UPSC civil services preliminary examination typically include being a citizen of India and holding a graduate degree from a recognized university. Candidates must be within the prescribed age limit, usually between 21 and 32 years, although certain relaxations apply for specific categories such as Scheduled Castes and OBCs. Additionally, candidates should ensure they meet the physical and medical standards set by the commission. Thorough familiarity with these criteria is essential for a smooth application process and avoiding disqualification.