Eric - Read "Tactics" by Greg Koukl
Tactics, by Gregory Kouhl, talks about how to defend yourself from objects to Christianity. He brings up a couple of techniques, the most important is what he calls the Columbo. In Summary, the Columbo is the art of asking questions, to either get more information from the other person, to force him/her to defend her claims, or to lead the conversation. Other techniques include the Steamroller, which talks about how to deal with someone that talks over you, and Rhodes Scholar, which deals with people who solely appeal to scientists and other 'smart' people.