IMO one of the smartest things you can do to try and be a better causal inference thinker is this: be mindful and sensitive to the fact that "looking harder means finding more."
In every domain, in every area of science, this is a very critical thing to understand, and very very difficult to remember because despite feeling simple it is actually very complicated.
This is particularly relevant in pressing concerns about e.g. viruses these days. We have developed better tools and we bring those tools to bear on a situation in the world and we observe phenomena that seem important. Yes, this observation matters.
But selection matters too. How much does the thing we observed exist in a different population? How much more likely are you to be observed if you are in the population of interest in the first place? These are critical inference questions.
There is a LOT of statistical theory and methodology about this. But you do not need to know anything about math to get better at the logic of it. Get good at the simple logic of it and you will be better than a lot of people in a lot of rooms trying to interpret a lot of data, I promise you.
What are we comparing to what? Who had the opportunity to be observed and who did not? How did we change the method of observation?
An insidious variant is: how did we choose to observe at all?
