There are few points which you can consider -

1. Know the syllabus very well

2. Make a proper study plan

3. Get good preparation material like -

Physics - Concepts of Physics by H. C Verma Vol 1 and Vol 2 Problems in General Physics by I.E. Irodov.

Chemistry - Atkins' Physical Chemistry Physical Chemistry by N Awasthi.

Mathematics - Higher Algebra by Hall Knight+ Bernard-child Differential Calculus by Arihant.

(a) English Proficiency - BITSAT English Proficiency & Logical Reasoning by Disha Experts

(b) Logical Reasoning - The Pearson Complete Guide to the BITSAT (English) by One Learn Education, Wren and Martin.

4. Make Short Notes

5. Take help from Sample papers and mock tests.

To check the complete preparation tips, you can go through the below tips -

How to prepare for BITSAT 2018?

Good Luck!!!