Common mistakes made by first-time UPSC candidates include inadequate time management, failing to read the syllabus thoroughly, and neglecting current affairs. Many candidates also tend to focus excessively on one subject while under-preparing for others. Additionally, they may overlook the importance of writing practice for the Mains exam or ignore the value of revisions. Lastly, not seeking help or feedback can lead to missed opportunities for improvement. Recognizing these pitfalls early can help candidates navigate their preparation more effectively.