Ask HN: How do you identify premium checks in Android app when learning modding?

I’m new to Android app modding and still learning the basics. I’m trying to understand how people usually find where premium or paid features are enforced in an app. What kinds of keywords, patterns, or places in the code do experienced modders typically look for (e.g. strings, flags, checks)? Is it mostly about searching for specific words, or more about understanding app logic and flow?