Greetings,
Great that you are planning about scoring well from the start. I secured 96% in my 12th so I feel I am eligible to answer this question.
First of all, scoring 90% in State Board Exams are easy. You need to make sure that you take all the subjects very seriously and consider all of them to be equally important.
Keep revising whatever is being taught everyday. Make sure you keep writing notes / summary of all the concepts you read.
Don't memorize stuff just like that. Understand what is being asked in the questions and what the concepts are all about.
Make sure you finish your portions well in advance of your exams. A day before the exams, practice question papers and make sure that you write all the answers neatly and legibly.
For subjects like math, keep practising more and more questions.
All the Best!
Regards,
Chirag
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