I have only run into one other developer I know from the local community contributing to an open source project (not counting project devs/committers) on random occurence. Very few of open source software users contribute back to the projects. I think there is a huge amount of lurkers; people who observe the project but fail to contribute their own solutions back to the project when they encounter problems with the software (or lack of documentation).
I wrote this post while trying to get a Struts2 bug fixed. I'll keep real-life descriptions in italic font like this.
1. Identify your bugYou usually stumble on a bug when you're trying to use the component in some funny, modern, weird or alien way; integrating with another component, using rarely used/tested configuration, or simply using code from an unstable branch of the source code (bleeding edge).
The best way to isolate a bug is to recreate the conditions under which it occurs. The most handy way of writing this is by writing an executable test (a unit test if you will).
Is the bug already identified? Someone else might've had the exact same problem. Search mailing lists, issue tracker and the web in general to see if anyone else have been affected by the bug (and team up with them if so). There's no need to duplicate the identity of a bug.
I stumbled onto a bug when trying to unit-test my Struts actions' validation mechanisms. I have done so with the use of the ActionValidatorManager without problems in earlier version of Struts2 (WebWork). I searched the user-list and found another guy who has suffered the exact same problem some five days before. I added my own description of the problem to add some attention to the issue, adding some more details to the problem description, hoping that a project developer (dev) or experienced user would suggest a solution.
2. Get helpAsk around on the projects mailing list whether this is a real bug (try sticking to the user-list and not waste developer time if it's not a real issue). Many times developers or users will point out an error in your configuration, or tell you to upgrade to a later version of the component. If it is a real bug, they will probably ask you to file an issue in the issue tracker. Yes, you. Because you (the reporter) discovered the bug and you are probably the one best able to describe the problem and recognize when it has been fixed.
Three days after my mail to the thread mentioned, the problem was confirmed by Rich Thornett.
3. File an issue (document the bug)Most issue trackers guide you into providing the crucial details you should provide to describe the bug, including environment, configuration, component version, etc. I think the best way to describe a bug is by attaching a unit-test that recreates the bug. This isn't always easy, but still there is no better way to define a bug and have a fine-grained definition of whether the bug has been fixed or not. The test is either green or red. Those of you who already do test-driven development (TDD) will recognize this step. Those of you who don't, well, get a book and figure out TDD.
Rich did us the favor of filing the issue, so I didn't have to do much at this point. I eventually (today) attached a unit-test to the issue that might get patched into the Struts2 code so the error will not reoccur in the future. I discovered that this is not really a bug if you take the effort of using the StrutsTestCase in your unit-tests, but I found a new bug being problems integrating the StrutsTestCase with the Spring objectFactory. I'll look into this later.
4. Fix the issue (submit a patch)This is where the lazy ones quit. A project developer might be able to fix the bug in 2 minutes, so it's definitely an easy option to leave it to'em. However, if no one else suffers the effect of the bug, it will not be prioritized by the devs and it might be up to yourself to fix the bug. So get the code out! We're talking trunk-code that should be easily available from the projects SVN or CVS repository.
At this point I want to add to you anti-Mavenizers out there, this is where the advantage of Maven comes in full. I can get the code up and running in my Eclipse in 2 minutes since they use Maven. I don't have to read a friggin out-of-date developer guide before figuring out how to dev the code, spending an hour getting the deps right, then configuring them into Eclipse. Having a mavenized project makes it easier for others to submit patches to your project!
Have a look at the existing unit-tests that exist in the project. Now, for a moment (or more likely a few hours), pretend that you are a project developer and create a unit-test that isolates your bug if you didn't do so already when filing the issue). Finally, start debugging! Try to minimize the structural changes done to the source-code. This will increase the chances of the project devs absorbing your patch into the trunk-code.
In the Struts2 case, I haven't found this solution. I will continue to work on it, but hopefully it will attract enough buzz to get the devs interested and speed up the process.