I think the real answers are unsatisfying but unfortunately true:

1. Time. In the moment it's very hard to understand what's going on. Time gives perspective. The down-side to this is that raw data sometimes gets lost with time, and then the fights begin about how to interpret what data there are.

2. Judgment. In the moment, you have to use a combination of historical track record of the data source and your own judgment. New York Governor Cuomo did a good job of explaining the subtleties of this at his daily briefing yesterday (Saturday), which I recommend watching. In summary, there are certain things doctors and the WHO thought were true and recommended several months ago that turned out not to be true, and new information and policy recommendations get disseminated as we learn more.