Common resources used for subject-wise preparation for UPSC include NCERT textbooks, standard reference books, newspaper subscriptions like The Hindu, and online platforms offering study materials and mock tests. Additionally, coaching institutes provide structured learning and guidance. Various online forums and apps facilitate group discussions, helping candidates clarify doubts and stay updated with current affairs. Podcasts and video lectures can also be beneficial in providing diverse perspectives and insights on difficult topics. Thus, a well-rounded approach utilizing multiple resources is essential for effective preparation.