I have long maintained that testing is ultimately about thinking. A lot of your work is going to be predicated upon spotting incongruous elements (whether in documents or application code), resolving potential ambiguities in what you read or see, and dealing with potential inconsistencies or outright contradictions. Sometimes people will frame problems in such a way that your ability to “solve” or deal with the problem effectively is compromised from the start.

A good way to practice your thinking skills is to apply them in an entirely different arena than software testing.