The state you gave your 12th examination will be your home state for Jee main.

There is an NIT in every state in India. so,50% seats of an institute are reserved for the home state students.Same AIR is used to prefer the eligible student for a seat.

The candidate who satisfies the preferential measures like caste etc,.along with home state quota will be given first preference.

In this same criteria for seat filling is applied like obc/sc/st category.

Moreover the preferences of choice filling matters here so be careful and calculated while doing this.

All the best.