My tip to every developer:

Reading sample code is not enough to understand how it works. To develop a true understanding, you need to actually run the code and tinker with it. With the additions of comments and instructions, sample code is packaged to be easily digestible by the reader; but in reality, it’s pretty difficult to replicate from scratch. Reading is not the same as understanding, and actually trying to write the code yourself, or at least running it, will facilitate the learning process much more.