Hello Ankit,

If you want to get upto 95% in 12th class, and not having studied in 11th. It is going to be tough. You need to attend every class and pay maximum attention while taking notes in class and re-reading once you get home.

Clear all your distractions phone,television or computers/laptops. Go out for a walk regularly to practice mindfullness. Try Meditation. 

If you want to join a coaching center for an entrance exam, don't. It is very hard to manage both.

Hope that helps and feel free to ask if you have any more queries. Best of luck!

Hey Ankit,
It is totally fine if you didn't give much time to your studies in class 11th. It's never too late. You can begin now.
You need to first really motivate your self to buck up and cover up the loss you had in class 11th. Then focus on your basics first. Learn to manage your time and be dedicated and very much motivated, as once you start to think that you can, half way is already covered.
Set a goal for yourself in daily basis. Small goals will be the best to begin as they will help boost your confidence. Slowly increase your time of studying each subject. As your main aim is to secure good marks, try solving last year question papers once you finish a chapter. It will let you have an idea of questions plus help you in revision too. Questions in Science and maths subjects are usually of the same pattern, so when you solve papers you will have an idea of the type of questions. Manage your time well, stay healthy and give time to your recreation too. You will do good once you begin!
All the best! :)