For practicing or learning new coding things I like to read a projects source, run a debugger on it, and basically spend a couple days/weeks analyzing how every aspect of the system works. Then after I'm comfortable i.e. I can go through in my head for example the structs, their function calls, the system flow, etc, I try to program my own implementation of the system, a part of it, or a plugin. This has worked for me ,hopefully it helps :)