Now that 807 has pointed out the advantages I'd ride behind. Other than that, the few times I've introduced someone to cycling on the road I've always started by explaining the door zone and importance of riding out of it and, most of all, by teaching them how to emergency brake properly - hard on the front brake, back brake on the edge of a skid, weight back and arms strong. Hopefully I do this in a non-scary way, but I have a strong feeling that people should know how to brake.