Essential understandings of Indian society that UPSC candidates should incorporate into their preparation include awareness of cultural diversity, socio-economic disparities, and historical contexts that shape current issues. Knowledge of communal harmony, gender equity, and the role of various social movements is crucial for addressing sensitive topics. Familiarity with government policies impacting marginalized communities can also enhance candidates' perspectives. By understanding these complexities, aspirants can tackle relevant questions more effectively and contribute to informed discussions during interviews or written exams.