Scoring 250+ in JEE Mains is a difficult, yet achievable task. It is not true that you require special coaching to achieve these results. All you need to have is focus and determination. Yes, it is true that some teachers at your coaching institutes may provide valuable guidance and it is necessary to have mentors but most coaching institutes just rip off money from students. Here are the techniques that you should follow:

• Make a clear plan of what subjects and topics are you going to cover in the following years or months.
• Equip your bookshelf with books from various popular publishers and ask other JEE aspirants what books are they following.
• NCERT is necessary. Do not skip NCERT books as they build your base of the subject.
• Previous year question papers are most important. Solve as many question papers as you can. 
• Enroll yourself in a regular online test series. These series are available at low price on different websites. 
• Seek help of the people who have already cracked JEE with good scores and learn from them.
• Do not take stress and enjoy your preparation. 

Hello

You can definately score 250+ without coaching it isnt a big deal if you are dedicated.

Study everyday and make a time table, make sure that you stick to it and nothing can come in your way. Mke self notes of every subject purchase books that you need for Jee mains. Solve previous year papers buy 16 year arihant.Keep motivating yourself(Most Important).

And keep changing subject to study since it might get boring to study the same subject.

Revise the things you studied after 2 days and challange yourself if you remembered it all.

Hope this helps