UPSC aspirants prioritize their syllabus by first analyzing the weightage of topics in the exam and then creating a hierarchical schedule that dedicates more time to high-yield areas. They often use previous years' papers to identify recurring themes and adjust their focus accordingly. Additionally, breaking the syllabus into smaller, manageable parts and utilizing a mix of resources, such as books, lectures, and online courses, helps ensure comprehensive coverage without being overwhelmed. Regular self-assessments can also guide them in identifying areas needing further attention.