Hello Rajendra,these are some tips to prepare in IIT exam :

1.Prepare the basic concepts from NCERT

2.Do concepts fundamentals from standard books.Especially in physics and maths.In chemistry NCERT foundation is best

3.Practice questions from question bank.

4.Revise the difficult qusetion on a monthly basis.

5.For heavy concepts reffered youtube educational video.

6.Atleast 4 hours on concept building and solving question from the book especially MCQ

7.Atleast 1 hours for question bank solving which make familiar with actual exam

For more prepartion tips regarding BITSAT follow this link:https://engineering.careers360.com/articles/how-prepare-for-bitsat

Information regarding books:

List of Books for Chemistry 
1. Physical Chemistry by P. Bahadur
2. Organic Chemistry by Arihant (Theory & Practice)
3. Inorganic Chemistry by O. P. Tandon
List of Books for Physics 
1. Fundamentals of Physics- V. K. Mehta

Hi 

Best books for IIT 

Physical chemistry :

1)o.p tandon 

2) p.bahadur and NCERT (first preference ).

Organic chemistry 

1) o.p tandon 

2)Paula bruice .

Inorgainc chemistry 

1) NCERT and o.p.tandon .

For physics H.C Verma is the first preference .

And for mathematics : syllabus wise best books are available ..prepare class 11 and 12 the class. Books.

Arihant publication new pattern for mathematics. jee mains

Thanks.