Hello again,

• Start revising all the topics of class 9th and 10th finished by you.
• Schedule your studies everyday so that no subject goes unprepared.
• While studying, make notes of the important points. You can go through them before the exam day.
• Solve as many sample papers as you can. These will make you familiar with the exam pattern, marking scheme followed in the exam.
• Eat good and healthy food.
• Exercise regularly.
• Take proper rest as this will refresh and rejuvenate you.

All the best!

You should join coaching institutions and get doubts cleares and strengthen your fundamental which is essential. Study from Right books like NCERt curriculum and revise all questions asked previously. Practice as much a syou can daily devote fixed schedule for preparation.

All expeet tips compiled below. 

https://school.careers360.com/articles/ntse-preparation-time-planning-for-answering-each-segment-crucial-says-girish-sachdev-study