sir at present i am in class 9th i m interested in iit. can u guide me that how should i study .this year i got 10cgpa

@ ishita 
GREAT work .. i appreciate your effort in class, as u have got 10 cgpa , but let me to tell that this cgpa doesnot depend upon the ranks and qualification status for iit . 
so, as u are in class 9^th , frst of all study ncert twice and clear your fundamental , 
that will matter much in class 11^th .now, go for the olympiand s, ntse and other competetive exams , which will give u the boost that like which type of questions are coming in entrances , 
after that read the S. CHand and R.s agarwal books , they will have better concept , u can even take askiitian package , they are simply awesome , 
and donot loose focus on study , study is a constant thing , at this point of time that is sufficient , and once you will enter 11^th class , the real war will start , 
now , donot take much stress, just clear your concepts and fundamental , and practice HOTS questions given in the ref books . 
HOPE IT CLEARS YOUR DOUBT 

ALL THE BEST ..