I always hear that involving with open source projects is good for career and the more (good) open source you release, the closer you will be to getting your dream job before you've even had an interview.

I am expert in Java and I am trying to become fluent in Scala. I always think about getting involved in open source development in Java/Scala but the following confusions stopping me to do so.

How/where do I start in open source development projects in GitHub etc? Or How to find active/busy open source development projects? How to find an area where improvement is required or enhancement required in such projects? It looks too complex in the first analysis or its pretty hard to find such opportunities. What are the common strategies to follow if I want to become hobbyist/free time open source developer?

People who have experience in open source development please share your learnings/expertise from scratch.

Thanks in advance.