Once you have looked at the information, start asking yourself the hard questions: Do I have a clear picture in my head of the situation I am facing? What parts of the picture seem the clearest? Are those clear parts actually untested assumptions? How can I test those assumptions?
You need to question every single assumption: How do I know that? What is my source of information? Is that a reliable source? Is there another source? Does it fit with common sense? Does it fit with everything else I know? Am I sure? How sure am I?
The point of such interrogation is to figure out what you definitely don’t know so you can be clear on what facts you need to uncover.