Strategies to boost confidence before the UPSC interview include thorough preparation and self-reflection. Candidates should familiarize themselves with their application, current affairs, and general topics relevant to the civil services. Practicing mock interviews with peers or mentors can simulate the actual experience and identify areas for improvement. Focusing on body language, articulation, and critical thinking during these practices further builds confidence. Additionally, engaging in relaxation techniques such as breathing exercises is beneficial in managing anxiety, ensuring aspirants present their best selves during the interview.