Techniques to enhance memory for vast topics in UPSC preparation include using mnemonic devices, mind mapping, and spaced repetition. Mnemonics aid in recalling complex information through creative associations. Mind mapping visually organizes information, enabling better understanding and retention of relationships between concepts. Spaced repetition helps reinforce learning by reviewing material at increasing intervals, solidifying knowledge over time. Additionally, summarizing content and teaching it to others can further strengthen understanding and recall. These techniques create a robust study framework that maximizes knowledge retention for the exam.