1. Make the Christian commit to defending one particular date (century) for the Exodus.
If you do not do this, Christians will pull “evidence” to support different aspects of the Exodus story from different time periods and expect you to still accept that they have presented evidence for ONE Exodus.
2. Make the Christian select one geographic location for the Forty Years of Wandering, and one geographic location for Kadesh-Barnea.
In my recent debate, I had Christians positing the Wandering took place in Saudi Arabia and that Kadesh-Barnea was in Trans-Jordan, not in the Sinai.
3. Make the Christian commit to a specific English translation of the Hebrew text.
For instance, and most importantly: Does the Christian accept that “six hundred thousand Hebrew fighting men and their families” left Egypt, or, does the Christian reinterpret the text to say that “six hundred families” left Egypt. Big difference. The choice of translation determines whether archeologists should be looking for evidence of two to three million people or two to three thousand people.
4. Lastly, ask the Christian if he believes in biblical inerrancy: that the Bible cannot be wrong.
If your Christian is an inerrantist, no matter what evidence you present to him, he will hand-wave it away. Your discussion with him is futile. The only possible benefit of debating an inerrantist on the Exodus or any other discrepancy in the Bible is to demonstrate to “lurkers” following the discussion, just how ridiculous and nonsensical it is to believe that any human text is “perfect and without error”.