I am currently studying in 9th. In which year should I appear for the NEET and what are the preparations I should do to score 600+ marks?

You are studying in 9th, well most likely you will be answering NEET IN 2023 or 2024, i.e, after u have given 12th boards. If you are interested to crack NEET then you should do your studies regularly. If possible join a coaching institute like Aakash or Allen and start your preparations from now on. Make sure you focus well. Institutes nowadays focus mainly on NTSE scholarship as you are below 10th standard, so you should prepare well. If your focus lies in medical only make NCERT text books your Bible. Follow your coaching. And you will do well. Good luck