Some of the issues on the issue tracker are marked with the "Newbie" label. If you're interesting in contributing to Storm but don't know where to begin, these are good issues to start with. These issues are a great way to get your feet wet with learning the codebase because they require learning about only an isolated portion of the codebase and are a relatively small amount of work.
The Implementation docs section of the wiki gives detailed walkthroughs of the codebase. Reading through these docs is highly recommended to understand the codebase.
Contributions to the Storm codebase should be sent as GitHub pull requests. If there's any problems to the pull request we can iterate on it using GitHub's commenting features.
For small patches, feel free to submit pull requests directly for them. For larger contributions, please use the following process. The idea behind this process is to prevent any wasted work and catch design issues early on:
Documentation contributions are very welcome! The best way to send contributions is as emails through the mailing list.