Some concrete steps you can take to become a contributor to an open source project:
- Download the binary and source distributions of the project
- Subscribe to both the user and developers mailing lists for the project
- Read all the provided documentation. In addition to what's provided with the distribution there may be more information on the website, including on a Wiki.
- Read the questions and answers on the lists, and also the commit messages that show changes to the source code. (You may have to sign up for a third list to get these.)
- Learn to build the project from the source code. (This should be possible with the "source" distribution, but if not you'll need to learn how to get the project's source code from the repository.)
- Play with the examples, then run them in a debugger and step through the code to see what really happens.
- Look at the unit tests for the project. See if there is a code coverage report, probably on the website, and look for areas that need more tests.
- Either add something to the provided examples, or try to write your own code that uses the project.
- Ask [smart questions] on the appropriate mailing list.
- Answer questions on the user list.
- Offer opinions on topics on the developers list.
- Review the list of open bugs for the project and comment on (or vote for) the ones you feel would be useful.
- Try to implement a solution for one of the open bugs. Attach your patch to the bug ticket.
- Open bug tickets for any problems you find. (Depending on the project, it may be customary to bring the topic up on the mailing list first to see if it's really a bug.)