In my experience, find something you want to find out about a software, and then do that. For example I wanted to write an autosplitter (used for speedrunning) for the witcher 3. So I first had to figure out a plan. I found out that witcher3 is heavily based on facts, and fact-changes. If you progress a quest, thats an entry to the fact-database. I went looking for the method which adds facts to the db, and after a while I found it. Then I hooked it (redirected it to a custom function, which calls the original after my custom code executed), and wrote the rest of the autosplitter.