Below are the listed point you should follow for prepare for iit

Time Management. ...

Follow a Schedule, Make a Plan. ...

Know the syllabus and the exam pattern well (including weightage) ...

Coaching Classes  Online or Offline? ...

Study concepts, solve problems, look at solutions. ...

Solve previous years' papers

Feel free to comment if you have any doubt
Good luck

Hello

First Steps

The very first step is to get focused. Your final result is a comparative rank against long term planners, who have been preparing months, if not years. Only a concentrated, industrious, and planned study plan will yield the desired score and rank.Focus on improving your problem-solving speed, which requires continuous practice. Drill yourself with regular numerical problem practice. By the time you go for the actual exam, you will have developed a knack for recognizing the type of problem at once, just by looking at it.

Mathematics:

Make sure you can solve problems from the NCERT class XI and class XII textbooks.For best concepts, use IIT Mathematics for JEE (Main and Advanced) by M.L. KhannaFor the most abundant supply of difficult questions: New Pattern IITJEE Mathematics by Dr. S.K. GoyalPlane Trigonometry and Elements of Coordinate Geometry by S.L. Loney

Physics:

Concepts of Physics, Volumes 1 and 2, by H.C. VermaProblems in General Physics, by I.E. IrodovFundamentals of Physics, by Halliday, Resnick, and WalkerUnderstanding Physics for JEE Main and Advanced (series), by D.C. Pandey

Chemistry:

Study the NCERT chemistry textbooks for classes XI and XII.Organic Chemistry, by Morrison and BoydNumerical Chemistry for JEE Main and Advanced, by P. BahadurConcise Inorganic Chemistry, by J.D. LeeModern Approach to Chemical Calculations, by R.C. MukherjeePhysical Chemistry, by P. Bahadur.

And if books are not helping then try online test practice . It will help you to identify your weaker area and at the same time it will increase your accuracy level as well.

I hope it will help you
Good luck...