MacOS X manually remove apps and associated files

Today I was trying to compare Appzapper vs Appcleaner and see which app removes unwanted app and its associated files better. After some reading and I found that the best method is still removing them manually. But how do you know which files specifically in used by the app you intended to get rid of? Here is a method I found posted by GGJstudios in MacRumors forum that will come handy if we really need to look into it.

Here is the link : To manually remove an application and all associated files