The ranking of candidates in the UPSC Civil Services Examination is determined by various factors. Primarily, it hinges on the performance in both the Preliminary and Mains examinations, along with the interview. Each component contributes to an aggregate score, which ultimately decides the rank. Additionally, the number of vacancies in specific services and the overall difficulty level of the exam can influence rankings. Other influential aspects include the candidate's ability to handle the vast syllabus efficiently, time management skills, and strategic preparation that encompasses revision and practice.