Anyone can contribute to Chrome OS, even if you aren't a developer.
Chrome OS is a famously user-driven project. Its humble beginnings started when the Chrome Team sent preview Chromebooks to interested users across the world, and ever since the team has been very open to user submitted feedback.
No matter how technology savvy you are, there's a way for everyone to get involved.
Chrome OS has a built-in feedback tool that can easily be accessed to report an issue or to just provide general thoughts on how specific functionality could be improved. You can invoke the tool either by visiting Menu -> Report an Issue or by the key combination Alt+Shift+I.
Technology savvy users may want to help beta test new versions of Chrome OS by switching to the beta release channel. In this mode, it is expected that you'll be on the look out for bugs, and if you spot any, that you'll report them to the team using the built-in tool. By being a beta tester, you can help make Chrome OS a better product for everyone.
To switch to the beta release channel, visit chrome://help, select "More info...", and then click "Change channel..".
Note: There is also a "developer" release channel, which is considered experimental and very unstable. It's primarily designed to let developers check out the latest changes so they can prepare their applications to be compatible.
Bilingual users can help correct mistranslated text in Chrome OS by filing bug tickets directly to the Chromium Tracker.
The Chrome OS Community is growing daily, and you can play a key role in helping new users get started with the platform. There are no formal requirements for this task, just a willingness to solve problems and assist users. The official support forum, Chromebook Central, has a program that rewards "Top Contributors" for their efforts.
There are many new bug tickets submitted each day to the Chromium Tracker, and they all need to be properly organized. This can be done partly be volunteers who spend time building up a good understanding of the project tracker (the various categories, which team members handle which categories, etc.). If you spend enough time doing this type of work, you can even be awarded with an official @chromium.org email address and elevated permissions.
If you're a developer looking to get started with Chrome OS, there's much more to know than we could possibly provide here. Instead, we recommend looking at the official documentation provided by the team.