Contributing to open source is, to me, very similar to learning a language at work. The difference is that you seldom have the chance to learn a new language at

Contributing to open source is, to me, very similar to learning a language at work. The difference is that you seldom have the chance to learn a new language at work because you generally have to first be experienced with it. To me, I always learn the best when there's a necessity to ship my code. Side projects won't do, and I always revert to using my skills developed at work. Therefore, this sounds like a very good piece of advice to start with.