Favorite technique: Argue with yourself about your conclusions.
By which I mean if I have any reasonable doubt about some idea, belief, or plan I split my mind into two debaters who take opposite sides of the issue, each of which wants to win and I use my natural competitiveness to drive insight into an issue.
I think the accustomed use of this would be investigating my deeply held beliefs and trying to get to their real weak points, but it is also useful for:
Examining my favored explanation of a set of data
Figuring out whether I need to change the way I’m presenting a set of data after I have already sunk costs into making the visualizations
Understanding my partner’s perspective after an argument.
Preparing for expected real life arguments
Force myself to understand an issue better, even when I don’t expect I will change my mind about it.
Questioning whether the way I acted in a situation was acceptable.
An exercise in analytic thinking.
Evaluating two plausible arguments I’ve heard but don’t have any particularly strong feelings on
Deciding whether to make a purchase
Comparing two alternative plans