The most important constitutional amendments that every UPSC aspirant should know include the First Amendment (freedom of speech), the 73rd and 74th Amendments (Panchayati Raj and urban local governance), and the 86th Amendment (right to education). Understanding these enables candidates to grasp the evolution of governance and citizen rights in India. Other significant amendments include the 42nd Amendment (the 'mini-Constitution') and the 44th Amendment (protection of personal liberties). Awareness of these amendments is crucial for a well-rounded understanding of Indian democracy and its workings.