Vinny has been blogging about Ehrman's recent book on the historicity of Jesus and in this post discusses the parallels between mainstream economists and mainstream ancient historians on the Jesus question.
A commenter points to this helpful article that provides methods for evaluating the soundness of the mainstream consensus in various fields. Acceptance of scholarly consensus is a good starting point. But what characteristics would indicate that scholarly consensus in a given field is less reliable? How do the various disciplines fare? Check it out.