A good strategy for choosing an optional subject in UPSC is to prioritize personal interest and familiarity with the subject matter. Candidates should evaluate their academic background and strengths, opting for subjects they are passionate about, as this can enhance motivation during preparation. Additionally, assessing the subject's overlap with the General Studies syllabus is beneficial, ensuring maximum utility of study materials. Researching available resources and guidance, as well as analyzing past performance trends in the optional subject during examinations, can provide insights for informed decision-making that aligns with one's overall preparation strategy.