Dear Sripad,

Try to to as good as possible atleat cross 75 % ..

For IIT JEE  .. the first very important thing is clear and enhance your concepts  .. jus keep this thing in mind that building concepts and practicing a lot is damn important for IIT preparation..
Always start from BASICS because "without base, there will be no altitude…  Never prefer solutions of questions before doing SELF-ATTEMPT at least five times till you get the right answer because "without fall you can not stand at once". 

Study without loosing the concentration coz studying 2 hours with very good concentration is equals to studying 5-12 hours without any concentration. .  and  have a confidence in yourself.  

All the Best.