[Seanny123]

In my experience, the trick is finding the sweet spot between something you use every day and your abilities. I don't contribute to Ubuntu, because I have very little understanding of what's going on there. I do contribute to my lab's software Nengo and other libraries I use, because I understand the code layout and where I can contribute. Consequently, maybe it's a good idea to make a decision matrix based on these criteria?

[TrickyRick]

Yeah, this I think is the most important. You can't just pick up some OSS project and start working away, it's usually a lot easier if you've been a consumer of the project before. I've contributed a lot to several big JS projects (Webpack, Grunt, npm) because they were missing things which I needed and it turned out to be easy enough to just add them.