IIT JEE is a topmost competitive exam in India. Its syllabus is vast and competition is tough. Firstly make sure that you really have a passion for engineering, technology, research work etc. If not, then you need to reconsider the career options. Make a goal and make a study plan accordingly. Make sure you plan time for all the activities that will consume your time and energy. Keep a few hours for yourself too (sleep, exercise etc.)
Plan your study schedule systematically. Create a timeline for a two-year period. Keep the last three months for revision for IIT JEE exam. Allot time for topics and sub-topics of all the subjects and follow a balanced approach.
If you are joining a coaching class, make sure that you join a coaching class with good qualified and supportive faculty members. The advantage of joining a good coaching institute is that you can interact with teachers and students and keep your motivation level up.
Understand the concept deeply. Once you are confident about a topic, you can move on to the next one. If you read a question and know exactly how it can be solved in reasonable time, you can skip directly to the next question. A group of studious friends keeps you motivated. Discuss your ideas and problems with your friends.
If you fail to make it to the IIT, it is not the end. It is the time to evaluate your priorities once again. Do not get caught up with the problem, find a solution.
Stay positive, work hard and have patience. Good Luck !!!