Common mistakes made by UPSC aspirants during preparation include inadequate time management, lack of focus on current affairs, and insufficient revision. Many candidates tend to overemphasize optional subjects while neglecting General Studies or current events, which are integral to the examination. Others may fail to practice answer writing, leading to ineffective communication during Mains. Additionally, relying solely on one source for information can result in gaps in knowledge. Being aware of these pitfalls and adopting a comprehensive study approach can significantly improve an aspirant's chances of success.