This blogger has some good thoughts on how to win a debate. My favorite one was number one, posted below.
How to Win Any Debate… Even if You’re Less Intelligent, Less Prepared, and Less Attractive than Your Opponent « Meditations on Meaning
1. Winning Isn’t Really Winning
Many people think that a debate is about choosing a position and holding steadfastly to that position until, perhaps, an opponent breaks. But this is a very limiting view of winning, because it doesn’t allow for the kind of discussion that creates better options and better decisions. Winning isn’t about forcing our opinions down others’ throats with whatever rhetoric we can muster… it’s about creating an atmosphere for collaboration and change.
My opponent believed that winning meant arguing his position with “greater aplomb and dexterity”. He was right… provided that the guys in suits and ties were the only judges around. But there were a thousand people in the audience – none of whom knew the formal rules of debate – who decided on the de facto winner that afternoon. And, like me, they didn’t care what the suit-and-tie guys thought!