Hii,

To get seat in NIT's and IIT's  first of all you have to write JEE Mains exam and then JEE advanced. Your IPE marks will also matters a lot in getting a good college. You need to score more than 590 out of  600 in group Subjects. Your JEE percentile should be greater than 95. So you will get some good NIT's. If you want to go for IIT then write JEE advanced. A valid score in JEE advanced will lead you to IIT.