Hello Aspirant,
So you want to crack IIT. Avery good decision by you. Cracking IIT is not a one shot process. Continuous hard work and determination and dedication towards your studies is required. You should leave mugging up things and try to build up your concepts. Practice numericals as much as you can. Solve last year papers also to get familiar with the type of questions asked in examination. Focus and concentrate on all three subjects. Chemistry is scoring so you should be strong at that. Last but not the least take care of your health because healthy mind resides in healthy body.

All the very best !