The most commonly overlooked topics in UPSC exam preparation include areas such as environmental issues, social justice, and certain aspects of Indian history, particularly regional histories that are not well documented in mainstream resources. Candidates often focus heavily on current affairs and major historical events, neglecting the nuances of specific subjects or sub-topics. Additionally, subjects like science and technology and ethics may be deprioritized despite their relevance in current trends and ethical governance. Comprehensive coverage of these topics can significantly enhance a candidate's overall understanding and performance.