Stage one has 3 rounds:

Part 1- Menatl Ability Test

Part 2- Language Test

Part 3- Scholastic Aptitude Test

At Stage-I, selection is done at State or UT level through a written examination. After qualifying Stage-I a student appears for Stage-II, which is conducted by NCERT at national level. Every student who scores the required number of marks at Stage-II is eligible for the scholarship program.

You can check the detailed selection process for NTSE here .

Good Luck.