Hello ashutoash,

The best way to prepare organic chemistry is to practise more and more reactions. Just make a list of named reactions, preparations and other important reactions. Try learning it everyday, after that practise by writing them, and then solve previous year questions. Practise preparations and remember important points. For the theoritical part the only way is to learn again and again. Download the official syllabus of JEE main and learn only the specific topics. You may omit some topics that have low weightage or have'nt been asked in previous 10 years.

Hope this helps

Regards