[Question] If Rationality can be likened to a ‘Martial Art’, what would be the Forms?

In Martial Arts, we have ‘forms’ that allow us to practice our skills when not with a partner or in adversity. In Rationality, I imagine that this would take the form of “brain teasers”, but specifically regarding decision theory, overcoming biases, and calculating probabilities.

What are some things one can do to practice Applied Rationality? These can take the form of thought experiments, websites, apps, pen-and-paper tools, etc.

These would ideally range from “easy to do within a couple minutes” to “you need to dedicate a day to this”.