In order to start your preparation make sure you are aware of the complete syllabus and exam pattern.
You should go through previous year paper to understand the exam pattern and level of questions

Go through NCERT books for your preparation. So, that you have good hold on your basics.

If you are preparing for JEE Main you can easily crack BITSAT as syllabus is almost same only difference is that BITSAT have English Proficiency and Logical Reasoning section. You should read the newspaper daily to score good marks in this section.

BITSAT is a online test it is recommended to solve as many as mock test series for your practice and to analyze your preparation level at regular interval of time

Below are the important topics which you should focus more as it carries more weightage in the exam

Physics

Mechanics (Newton’s Laws, Work and Energy, Rotational Dynamics etc), Thermodynamics , Electrostatics and Electromagnetism.

Mathematics

Integral Calculus, Differential Calculus, Coordinate Geometry and Complex Numbers.

Chemistry

Ionic Equilibrium, Chemical Equilibrium and Gas Laws

All the Best for you Preparation!!

Hi,
Some of the important guidelines you can follow are:
Create a study plan for your preparation
Gather all the information about the official syllabus
Study for at least six to seven hours a day.
Add some time for breaks and other activities which can help to refresh.
Solve the previous year question papers and compare your answers with the given solved papers.
Practice only from those books which almost cover the entire syllabus of the exam
These are some of the basic yet important steps to do.

Some of the book materials you can refer to are: NCERT for all subjects are must!

BITSAT English Proficiency & Logical Reasoning PB (English) by Disha Experts
Comprehensive guide to BITSAT
BITSAT Complete Pack by Arihant
Physics by D.C Pandey
Maths by R.D Sharma
Pearson Complete Guide to BITSAT
These are some of the books you can refer to are.

Do not forget to go through previous year papers and mocks as they will help you to give the right direction to your preparation.

Hope this helps.
Good Luck.