I never did debate team or any of those “professional” arguing things, so I know very little about arguing. I do love it, however. I just want to point out two of the most common errors that people I have argued with make.
First and foremost, identifying the argument as part of one’s self will guarantee an unsuccessful and violent argument. If you can’t separate idea from self, you will not be capable of accepting the opposing position. So don’t argue. In my opinion, self exists entirely outside of ideas, and ideas in no way define self. Ideas are fleeting and open to massive change (or at least should be). Indeed, that’s the whole idea behind having an “open mind.” Anyway, if you learn to defend your ideas without feeling that you are defending your self, you will be much more successful. And, perhaps more important, you will also be more open to changing your ideas and opinions.
The second, and most obvious, is losing cool. This, of course, often goes hand-in-hand with the previous item. Frustration is nearly guaranteed during an argument, especially a highly polar one. Annoyance too. By letting these things get to you and becoming angry, you will likely resort to emotional arguments and personal attacks. This is not only socially dangerous and unwelcome, but also weakens your side of the argument. When you feel yourself losing your cool, you just need to stop and figure out why. Once you have done that, you can drive the emotion out of your argument and maintain a fair chance of winning (and of retaining friendships).