Hi, the main tip for BITSAT is while gearing up for BITSAT, don't waste time solving lengthier questions, but root for questions which are more concept based. You must have all formulas and equations (algebraic and chemical alike) on your fingertips.

Also SPEED is the key for BITSAT entrance.
You will also have to focus on mocks which are sectional or full length. But this will help you to review your performance in the exam.

Focus on NCERT for PCM. Some reference material shall be required.
Hope this helps.
Good Luck.