Maths :- There are generally two classes of people in this category - those who are good at it and those who are not. Those falling into the first one would leverage a tough Maths paper to score high in the JEE rankings. For those who are relatively weaker in Maths need to prioritize - attempt their relatively stronger areas in Maths first before taking up the weaker ones. This will help you to clear the cut off marks. Having said that you should compensate the "loss" in Maths by scoring high in other subjects.
For me, I have always loved Maths and it has been my forte :-). Mathematics helped in putting me in the top ranks.