This is a subject of some interest to me, as I have been surrounded by political discussions since my birth and have contributed a small mite myself. Indeed, it has been pointed out to me that in some ways (not in political views but in attitude to discussion) I resemble the Cambridge professor in Tom Stoppard's last play, "Rock and roll".
So, naturally, I find it interesting when other people blog on the subject. Here is one of my favourite American bloggers, Neo-neocon, discussing how to conduct debates. She also links to an old but supremely relevant article by Owen Harries. There are also some genuinely interesting and thoughtful comments. Enjoy.