How to Contribute to Apache Hadoop Projects, in 24 Minutes by Justin Kestelyn.
From the webpage:
So, you want to report a bug, propose a new feature, or contribute code or doc to Apache Hadoop (or a related project), but you don’t know what to do and where to start? Don’t worry, you’re not alone.
Let us help: in this 24-minute screencast, Clouderan Jeff Bean (@jwfbean) offers a step-by-step tutorial that explains why and how to contribute. Apache JIRA ninjas need not view, but anyone else with slight (or less) familiarity with that curious beast will find this information very helpful.
I have mentioned a number of Hadoop ecosystem projects and this is a nice overview of how to contribute to those projects.
Other than the examples, the advice is generally useful for any Apache project (or other projects for that matter).
I first saw this in a tweet from Cloudera.