I think a good measure (though not foolproof) is whether or not you have actually changed or altered your positions after presented evidence.
Most definitely, If I wasn't challenging and modifying my own assumptions at least a couple of times a week I'd suspect something was wrong.
IMHO it all starts by understanding a few things:
(all my opinions based on my own experience, mileage may vary)
1) rank-and-file Democrats are not evil people, they are good people that want the same thing that everybody wants, specifically whats best for our Country and it's people, same goes for rank-and-file Republicans.
agreed
2) neither "side" has the best ideas on all issues, there's room for everybody to contribute to the problem solving process.
agreed
3) Always assume that any politician and any media outlet is lying until the preponderance of the objective evidence suggests otherwise.
Not quite. One may assume that the politician is spinning the truth and that the media may stretch it. But to assume that they are lying is a bit overdone. Not saying this is common, but I have a good bullshit detector.
We are better served by just understanding what motivates the speaker and judging the comments with that in mind.
4) Politicians don't have your best interests at heart, they have their own best interests at heart regardless of the letter behind their name.
Not always. There are public servants who are absolutely working for the public good. And I would say that many young politicians enter with the best intentions.
5) You do yourself and your country FAR more service by being critical of your own party than you do by being critical of the opposition party.
Or.....how about not having a party?
6) Feeding your confirmation bias only makes it stronger, starving it will eventually kill it off.
agreed
7) The truth is often in the last place you look and often speaks with the softest voice but it should be the only thing you're interested in finding.
Not sure about that. I find the truth quickly in most cases. When I don't know the truth of a matter, I don't open my trap about it.
8) Become "politically unreliable" that way neither party can take your vote for granted.