It is not possible after class12th But after Your graduation, you can go for Indian Airforce for short service commision and become pilot. Your training will be completely free Instead you will be given salary. It will not just serve Your dream but will also give a  chance to serve our country. After 14 years of service, You will retire and You cab Easily get a job in any commercial airline.

As of now, You don't need to do anything just complete Your graduation and for more information visit:

http://indianairforce.nic.in/content/career-and-recruitments