I assume you are talking about NEET.

You have a year to prepare for NEET 2020. It's a great thing you are aiming high. Start by studying basic concepts, especially in Chemistry and Physics which are very conceptual. Try to finish your syllabus (covering all chapters) by at most December. That way you'll have some 3-4 months to practice questions and solve past year papers. Solving past year questions are extremely important because it gives you a familiarity with the exam pattern and the type of questions you are gonna face in the exam.

Move to the question papers only after you have completed your syllabus because it'll be futile otherwise. For biology, keep revising chapters you've studied from time to time so as to not forget them.

If you can, buy a test series from a reputed institute (Allen, Resonance, Aakash etc) to practice regularly.

Write down important formulas and keep looking over them from time to time. Same with terms and definitions in Biology. Make your own short notes, because when you write something you remember it better.

Hope this helped. Good luck for NEET 2020.