Exam

The basic eligibility is as:
Candidates must have passed an under graduate degree from any institution/university recognized by law in India or, candidates who have diploma in UG design from NIFT/NID only, are eligible or, Candidates who have passed diploma course of three years from NIFT/NID are also eligible.

No Manu, it is tough to get the same. Use the below link to predict the colleges which you may get:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor.

The chances of getting NITs and IIITs are tough, however, you can click on the link below and check the same:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor.

Please refer to the link below and check out which colleges you can get:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor.

Kindly fill in your details in the link below, to find out the colleges, you can get into:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor

Please refer to the link below:
https://www.shiksha.com/b-tech/articles/how-to-calculate-jee-main-rank-from-percentile-blogId-19953
https://www.shiksha.com/engineering/articles/how-to-calculate-jee-main-percentile-score-know-normalization-process-blogId-19933
You can get detailed information on the same.

Why don't you use Shiksha college predictor?
JEE Mains rank and college predictor uses your JEE Main 2019 percentile to predict your rank and chances of admission in the college of your choice.
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor

Instead of seeking simple tips, please go through the CUSAT syllabus and prepare accordingly. Use the following for detailed syllabus:
https://cusat.cuchd.in/about-us/syllabus.php

JEE Mains is the criteria to take admission there. JEE Advance is mainly for IITs.