I participated in a formal debate (20-minute opening statements, followed by rebuttals, close, and Q&A with the audience) a couple of weeks ago. The topic was “Is it Reasonable to Believe in God?” and I summarized the details here. The organizers have now supplied the video, which I include below. I think there were more than 100 people in the audience (mostly Christians, I’m sure).
Everyone treated me with respect, and I had a great time. Watch the video and tell me what you thought (the quality of the video looks to me to be excellent).
Opposing arguments
My opponent was Rob van de Weghe, and he opened with four arguments.

1. Cosmological Argument. The universe began to exist; therefore, there must be a creator. A sub-argument was that entropy is increasing, so things must be winding down from a creation event.
2. Fine Tuning Argument. The universe is delicately tuned for life.
3. Design Argument. Life is complex, which points to a designer. A sub-argument was: where did life come from? God answers this question nicely.
4. Moral Argument. Each of us is wired with a standard of moral values—where did this standard come from except from God?

My thorough responses will be found in blog posts (search and ye shall find), or you can watch the video below to see my very abbreviated response.
Debate strategy and my opening arguments
It’s important to think out one’s goals. In a public debate like this, a technical win isn’t much of a goal in my opinion. If there were judges critiquing the arguments, I would be careful to respond thoroughly to every argument, defend any attacks on my own arguments, and make clear how I thought I was doing (“I notice that my opponent has said very little about my third argument, so I must conclude that he is conceding that point …”) to help the judges see how thoroughly I was winning.
But of course there was no formal judging. Instead, my Christian opponent provided a Christian audience for me to lecture to, and my primary goal was to give them some ideas they hadn’t considered. If they heard a few simple, memorable puzzles to which they had no snappy answers, that might get them thinking. This means that standard arguments (such as, “Why do bad things happen to good people?”) were out, since those in the audience would likely have heard rationalizations already. And I had to do all this while coming across as polite, thoughtful, and intelligent.
Here are my opening arguments (I’ve written about each one in the blog):

1. Historians Reject the Bible Story
2. Mormonism Beats Christianity
3. Because There’s a Map of World Religions
4. Christianity Relies on Indoctrination
5. The Natural Explanation Resolves the Puzzles Confronting Christians
6. All the Other Religions Are Nonsense
7. Jesus Is Just One More Dying and Rising God
8. Christianity Is Unfalsifiable
9. God Has No Impact on Reality

My debate goal was primarily to overwhelm my opponent with the quantity of arguments as well as mix up the list to add a few that I hadn’t used in prior debates so that simply watching previous debate videos wouldn’t give all my secrets. I read Rob’s book beforehand, and I assumed he’d done some preparation on me as well.
Rebuttals
Problem 1 would be being blindsided by a good argument that I’d never heard of before. Problem 2 would be getting an argument that I was familiar with and had even blogged about but for which I couldn’t remember the best points.
I’d almost welcome a bit of Problem 1, just to make life interesting and to give me something substantial to blog about later, but this didn’t happen. To avoid Problem 2, I went into the debate with printed summaries of about forty issues, distilled down from my blog posts, anticipating what might come up. Rob’s arguments were on any apologist’s top-ten list, so I was able to pull out a summary sheet for each one and circle the points that I wanted to make in my rebuttal. This made my life much easier, and it is quite satisfying to be able to say something like, “Rob quoted cosmologist Alexander Vilenkin, but let me point out something else that Vilenkin said, and I quote …”
I’d like to thank the atheist friends who made the long trip to see the proceedings!
Feedback is welcome. Let me know what you think I need to work on—presentation, arguments, attitude, whatever.

To conceal a want of real ideas,
many make for themselves an imposing apparatus of long compound words,
intricate flourishes and phrases … new and unheard-of expressions,
all of which together furnish an extremely difficult jargon that sounds very learned.
Yet with all this they say—just nothing.
— Arthur Schopenhauer

Image credit: Steve Maw, flickr, CC