Well can't say about important chapter but  yeah can share some preparation tips

chemistry

give extra attention to inorganic chemistry

Be thorough with the formula of physical chemistry

Understand complete reaction and mechanism

physics.

Physics has more to offer than just numerical, there are important concepts behind those calculations which help in solving the questions with ease. Numerical only get better if you have done your preparation well by learning all formulae and theories which explain the logic for those numeric problems. So focus on understanding the subject than just viewing it as mathematics

maths

Practice, Practice and More Practice

As much of a genius, you might be, but there is no alternative to study maths than practice it day and night. Practice makes a man perfect and that's the only mantra which will make you excel in math section in KIITEE. Every problem has its own set of concept and probably multiple ways to be solved. The art of problem-solving only comes by practice and nothing else.

Make you own Notes

Maths is full of Formulae, theorems, abbreviations, symbols and allot more terminologies. Making your own notes will not help you recall them all at the time of solving a complex problem. One can make steps to solving a problem or short tricks to solve the questions fast.

Master your basics

It is better to master your basics than moving ahead without actually learning anything. Mastering your basics will help you in understanding the subject well. Moreover, it will make it easier for you to quickly move on with your practice.