Science and Policies key to it
Go away from politics and for shit sake give farmers machine to avoid crops residue burning.
Air filter tower (why not? if million dollars statues can be made, why not this?)
For time being subsidy to residents for Delhi to buy air purifier
And all other things mentioned in other answer:
1 Person to plant 1 Tree every 1 week.
Reduce vehicles emitting shits.
Policies like Odd-Even.
Stop entertaining your kids demands of crackers!