Find a closely held belief that you have. Say you believe (correctly) that Team Fortress 2 is the best online multiplayer game ever made. Now, open an incognito browser and search for, in my case, "Team Fortress 2 sucks." I look for someone who can convey thoughts in a clever way, who is entertaining and makes me go "OK you have a point there." Do this for everything that you like. It won't change your mind (in most cases) but it will let you know what the "opposition" so to speak is saying. And if you are going to argue about something, you need to know what the opposition is saying. This is how I came across William Saffire and William H Buckley. I disagree with about 90% of the things they say, but by reading them, I was able to defend my own beliefs better.