Can you please clear your doubt?

Are you asking if you start your preparation for JEE Main in 12th class will you able to crack your exam?

If you start your preparation in class 12th you have enough time to prepare for your exam you should plan your study accordingly

In order to start your preparation you should be aware of exam pattern and syllabus of the exam.

You can set your time-table according to your comfort. Set your daily and weekly targets and try to acheive them.

If you want to score good marks in JEE make sure your basics are clear. Make sure you read NCERT books throughly. So, that you can solve tricky questions easily.

You should focus on important topics more. You can solve as many as MCQs. For exam pattern and to know level of questions you can refer previous year papers.

Solve complete mock test series to work on your time management and to increase your speed. With the help of mock test series you can analyze your preparation level and you will get to know your strength and weakness. So, you can work upon them.

Revision plays very important role in scoring good marks. You should revise your syllabus properly. You can make your important notes as well which will help you in revision.

All the best for your preparation!!