Think up two reasons how your starting judgment could be wrong
This technique helps against a range of biases, at least including:
- overconfidence
- hindsight bias
- anchoring
- …
That many biases reduced, if you just think up some reasons that your initial judgment might be incorrect.
Although don't dwell too long:
After a certain point, it becomes increasingly difficult for a person to generate reasons they might have been incorrect. This then serves to convince them that their idea must be right, otherwise it would be easier to come up with reasons against the claim. At this point, the technique ceases to have a debiasing effect. While the exact number of reasons that one should consider is likely to differ from case to case, Sanna et. al. (2002) found a debiasing effect when subjects were asked to consider 2 reasons against their initial conclusion but not when they were asked to consider 10. Consequently, it seems plausible that the ideal number of arguments to consider will be closer to 2 than 10.
So consider the opposite but not too much.