In order to crack VIT and SRM it is very important that your basics should be clear. You should have strong hold on P/C/M subjects. You can refer NCERT books to make your concepts strong.

If you are preparing for JEE Main you can easily crack VIT and SRM exam. 

Give importance to the topics which carries more weightage in the exam. You can also solve MCQs related to them.

Generally, students are checked on the basis of concept, speed, accuracy, time management and decision making power. 

It is very important that you solve mock test series for your practice and to know your strength and weakness. So, that you can work upon them. 

Refer previous yaer papers to understand the exam apttern and level of the questions.

All the Best!!