Don't script anything. For God's sake don't script anything. I remember last year there was a group of girls who were debating in what sounds like a similar situation. They had written out everything each of them was going to say. They got good marks for it, but oh dear me it was boring. So, yeah, don't script.
Other than that, well I suppose you should remember to use reliable data and sources where possible. It's quite difficult to give pointers where you haven't provided much background but hey, I tried.