About my programming knowledge:

• I have basic knowledge of programming.
• Have never worked in a team project.
• Have done, only, a couple of small solo projects.

Problem:

Consider a typical open source project. We want to know about the project, so that we can contribute, test it, just out of curiosity, etc.

• The documentations do not describe the code architecture, usually, so RTFM(!) wouldn't apply here. They usually tend to describe how to use the software, not how it is designed.
• Mailing Lists in big projects are very crowded. Tens of e-mails are send in just an hour. also, following the mailing list to know the project is like understanding a film when you have arrived late, when half of the film is gone or even worse.
• Obviously, the code is not like a novel. So, you can't start from downloading the source code and just "start from the first page and so on"!

Question: How should one understand open source project?

What are the steps to do in an open source project, to understand how the whole thing works and get into speed with the "under the hood"?