I suggest checking out the git master and get familiar with the code-base. Our build is all maven-based, so it's easy to setup in the IDE of your choice (we use eclipse, though). Take a look in the "developer guide" on the wiki to get started.
Since Activiti is a big project with a lot of sub-modules, it off course depends on what you're interested in and what your strengths are. A good starting point is to look into the tests we currently have (and examples, in the src/test/java/…/examples) to see how the engine works internally. Next, you can pick an issue you feel comfortable with fixing from our JIRA and suggest a fix for it (make a pull-request on github, which we review).
Offcourse, don't forget to sign a contributor-agreement (see wiki)
Since Activiti is a big project with a lot of sub-modules, it off course depends on what you're interested in and what your strengths are. A good starting point is to look into the tests we currently have (and examples, in the src/test/java/…/examples) to see how the engine works internally. Next, you can pick an issue you feel comfortable with fixing from our JIRA and suggest a fix for it (make a pull-request on github, which we review).
Offcourse, don't forget to sign a contributor-agreement (see wiki)
