Common mistakes encountered by candidates during UPSC preparation include inadequate understanding of the syllabus, neglecting current affairs, and ineffective time management. Many aspirants tend to focus excessively on rote learning rather than developing analytical skills. Additionally, failing to take regular mock tests can hinder the assessment of progress. Over-reliance on coaching without self-study can lead to gaps in knowledge, while not following a structured study plan can result in inefficiencies. Addressing these mistakes is crucial for maximizing success in a competitive examination environment.