1. Teach the evidence for evolution.
2. Teach the meaning of "theory" in science.
3. Emphasize the difference between natural and supernatural explanations...
4. Recognize that, when it comes to science, we [meaning scientists] are the establishment [and so should not accept creationists as equals for debate purposes].
5. Educate yourself about the controversy.
He recommends the NCSE website.
I would add a #5: Explain why science and religion are not incompatible. I can't say it enough -a person can be a faithful Bible-believing Christian and accept evolutionary theory.
He ends by arguing passionately against religion. He does not accept my #5 at all and does believe religion is in direct opposition to rational science.
There are other videos available, but this is by far the most accessible and the most useful for folks involved in the evolutionary argument against creationism/id.
HT: AIG Busted