I see a url
I don't think there is a general answer to this. Given a web-page, you can idnetify main technolgies that are used by it. And then you need to understand the main scripts the page is laoding and relying on.
In other words, some of the urls are created and/or requested by the JS scripts so unless you understand the code and spend sometime on it, you may not be able to find out the origin of each url request/ajax call using the development tools like the one in chrome.
Overall, you need to have general idea of how main web technolgoies are working so that you can follow the url requests easily in practice.
I hope it helps.