This chapter examines what wisdom-of-crowds research tells us about the conditions under which a group of experts is more likely to come to a valid consensus. It summarizes four conditions for a wise crowd: selection for expertise, cognitive diversity, independence of judgements, and opportunity for sharing. It argues that the Delphi method comes closer to meeting these conditions than some other consensus methods and that the findings from wisdom-of-crowds research can be used to inform the design of better-quality Delphi studies.