The first and the most important thing to do is to be good at coding. The minimum qualification to become a Software Engineer at Google is not "Knowing how to code" but "to be good at coding". So make sure, you have a lot of practice in coding. You can participate in various coding contests. Then build projects based on the field you are interested in (Web Development, Android application, Artificial Intelligence, etc.). You can also start working as a Software Developer in a different company and then use that experience in your Resume. After this, you can start applying for a job at Google.