Here's what I do... I have a relatively-simple pet project that I understand thoroughly. When I decide to learn a new language, I do so by reimplementing the project in the new language. That way, I have a structure to the learning based on the project I fully understand. I then read/skip-through/hop-around books and other learning resources as I need to understand various components of the language to implement the features on the project. Here's one example implementation of it, which I need to write anew to learn Swift: https://itunes.apple.com/us/app/pyramids/id589550650?mt=12