Ask HN: How to start the freelancing career

I am a developer in India with about 13 years of experience. While primarily exp. it is around backend in Java/Scala, I am comfortable with React/Python/Apache Spark and distributed systems. Most of my exp. is in startups but working for large size companies for last 5 years. Being of introvert nature, I don't have many contacts outside my working groups / family.

I would like to start working as freelancer, and need suggestions for it. What should be my starting point, how to build contacts, should I work on Open Source or hobby projects and showcase them?