To enhance retention for UPSC, consider adopting the Feynman Technique. This involves teaching the material to someone else, which reinforces understanding. Additionally, using mnemonics and mind maps to visualize concepts can aid memory. Regularly revisiting notes through spaced repetition helps reinforce learning. Practice active recall by quizzing oneself instead of passive reading. Form study groups to discuss and challenge each other, promoting deeper engagement. Lastly, ensure to get adequate rest and incorporate physical activity to boost cognitive functions.