find another rational person who is either unbiased on the topic or even biased in the opposite direction

I do this with an imaginary person, since it's not very practical to find a person for every held thought and opinion heh.

I think one thing that has developed over many years for me is considering Both Sides of the Story - no matter what.

Even if it seems dumb or obvious.

E.g., I used to be staunchly anti-religious. Religious = Stupid. Simple as.

Nowadays, I'm much softer on that. I believe religion is not only necessary in the grand scheme, but a projection of something biologically innate. It's pretty damn liberating to the ol' brain to listen to both sides, and decrease one's dependence on any side at all.