Answers go out of date. A good question keeps paying you for years.

Facts have a shelf life, because the conditions that produced them keep changing. A question is different, since it is a tool rather than a result, and you can point it at every new situation you walk into. People who seem consistently perceptive usually carry a handful they ask everywhere. That is most of the trick.

Collect a question this week that opened something up, and keep it where you will see it. Try it somewhere it was not designed for. Over time you build a short list you can carry into any subject, which is worth more than anything you memorized.