Welcome to JavaRanch!
What are your interests? Get yourself familiar with the open source product first by using it, and join the community of a project that you can relate to.
You 'll have to build a relationship with the project, by taking baby steps
- subscribing to mail lists
- helping the user community
- helping the project with
testing and document writing
- helping the project team with solutions for open issues, providing patches
- ...
If you prove to be a strong community member, and you hang around long enough, you might become a committer.
Here are some links that discuss first steps to involvement:
http://jakarta.apache.org/site/contributing.html
http://cxf.apache.org/getting-involved.html
http://www.wikihow.com/Contribute-to-Open-Source (attention: lots of adds on this page, but read the 10 steps)
http://opensource.com/life/10/8/ready-be-open-source-contributor-dont-know-where-start
http://grokcode.com/108/6-easy-ways-to-get-started-programming-open-source/