Do you use Open Source software? Is there some software that's missing a feature you'd like to have? Is there some bug or annoyance that you could fix? What kind of project sparks your interest? Web? Desktop? Gaming? Drivers? Pick something you'd like to see done, then do it. Otherwise, pick project you're interested in, learn how to clone and compile it, then browse its Bugzilla/Issues and try to help them move the bugs forward. Translate something.