Hello anish
Physics is one of the scoring subject . Try to give as much time as you can . Clear your doubts and read theory as much as you can . Theory will help you to understand the basics and help you in problems also .
First solve the ncert because ncert clears doubts and have easy explanation . If you are facing problems and have doubts you can also find video lectures in youtube also . Physics is great subject . You can relate topics with you day today life . Just make you concepts and stick to basic . You will definitely be able to do good in iits and various other competitive exams. Most important thing in jee is speed and accuracy . Try to practise problems as much as you can . This will help you to analyse your preparation for exam . 
Jee is not so difficult if you have good concepts and have hold on topics .


Best of luck

Hello,
Even many are not good at it but they do score high marks by practicing a lot of questions..
You should start from basics and practice questions from NCERT BOOKS along with reading concepts.After completing NCERT BOOKS, you can follow HC VERMA books to practice numericals that might be helpful for solving questions in jee mains exam.Practice previous year's questions and analyse the pattern of exam.It's not that difficult to score good marks in physics in jee mains, only thing you should do is practice a lot.
Good luck.