Hi Ankit 

Best time to initially start preparing is after your class 10 as you start learning and clearing your basic concepts from that time only. Also you need to make proper schedule, choose right books, classes , study material. 

So firstly, revise your basic concepts of class 11th and 12th. Start studying 2-3 hours daily and if possible join some IIT-JEE coaching institute. 

And MOST IMPORTANTLY, keep checking latest information as JEE format has changed, so keep yourself updated with latest information . 

It's all about quality of your work , not quantity. Solving 30-40 difficult or tricky questions daily is much better than solving half a book daily. 

- right time to start for JEE preparation is when you feel like achieving or doing something passionately. hard work and smart work, both are equally important.

- focus on your weak points first and start working on them , practice as much as possible.

- Avoid shortcuts- there is no shortcut to success. Hard work is all you need. And do not depend on coaching classes. They'll help you but you have to study on your own as well. Self study is most important.

- make notes , mark your doubts and ask your teachers or mentors immediately. 

- manage your time. Do not spend half of your day in socialising. Avoid junk food and take good care of your health. Set your time limits for everything- studying, Using phone , going out etc. And do follow that routine. 

- practice previous year question papers and refer right books for JEE preparation. 

- But very firstly work on your conceptual clarity of fundamentals in Mathematics , physics and chemistry. Pay attention towards your mentors , teachers .

- No need to stuff your study table with end number of books. Choose right books based on your syllabus , you can also take help from online classes and check previous year question papers . Also, visit the website and check all the updated information related to exam pattern, syllabus etc. 

- Enjoy your journey of preparation. Do not let yourself down . If you think you are not able to solve more questions then just stop there and take a break. Try some mind relaxing activities like Meditation, yoga or read your favourite book or go out and play your favourite sport. And then come back and start again with full concentration. 

- so, for IIT-JEE preparation, you need Focus, Hard work, smart work and Say a Big NO to stress. If you think that you don't have much time to prepare and you badly want IIT then drop a year and start preparing NOW or else you can try for other exams. 

- so keep yourself Motivated and plan your activities based on your preferences. If IIT-JEE is your first and foremost preference, then just go for it. And try to solve tricky questions and focus more on your weak points. Do not focus on finishing end number of books. Instead, just see the quality of questions and try to solve them. Work hard but choose your books and questions smartly. 

All The Best!!