The Assertion and Reasoning questions asked in the AIIMS entrance will require you to be very clear with your basics and the important topics in Physics, Chemistry and Biology at a conceptual level. Mere rote learning will not suffice. The key is to be completely familiar with your NCERT textbooks, especially the ‘Points to Ponder’ sections and all statement containing the words ‘because’, ‘therefore’ and ‘hence’ in them. Focus on reading and revising your NCERT texts as much as possible as this will enable you think with complete clarity, help you ascertain the facts behind each statement, make relations between and solve the questions in quick time. Other recommended books for Assertion and Reasoning are those published by MTG, Aim4AIIMS, Errorless, Arihant and Bright. You can also use the modules published by coaching institutes. Constant practice and revision are key, so solve as many questions papers from previous years as you can while preparing with the study material of your choice.