Strategies for retaining vast amounts of information for the UPSC exam include employing effective memory techniques, such as mnemonics and visualization. Breaking down topics into smaller chunks and revisiting them periodically helps reinforce knowledge through spaced repetition. Creating summary notes and mind maps allows for better organization of complex information, making it easier to recall. Engaging in discussions and teaching concepts to peers further enhances retention. Regular self-assessment through quizzes and mock tests ensures that candidates identify and address knowledge gaps, improving overall retention capabilities.