Common mistakes in UPSC preparation include inadequate understanding of the syllabus, relying too heavily on coaching instead of self-study, and poor time management. Many aspirants often neglect current affairs or fail to interlink topics, which is crucial for a holistic perspective. Rote learning without application can hinder performance, particularly in the analytical sections. Additionally, irregular revisions lead to forgetfulness. It's important to maintain a balanced approach, seeking guidance while fostering self-sufficiency in research and comprehension of subjects.