Previous year papers help you to know the level of the questions & also help to know the difficulty level of the exam. Here are some preparation tips you can follow  for the exam preparation.

Study as per the syllabus: There isn’t much of a difference in the syllabus for JEE and BITSAT, when it comes to Mathematics, Physics and Chemistry. What makes BITSAT unique, however, is the section on Logical Reasoning and English Language.

Online Mock Test: Take online mock test regularly to analyze your performance level and to know your strength and weakness.

Read good newspaper: To make the best use of the 25 questions, do make it a habit of reading a good national newspaper on a daily basis.
You can check the syllabus with the given below link.

https://engineering.careers360.com/articles/bitsat-syllabus

Good Luck!