Another RAND monograph on scenario design by H.A. DeWeerd, but this one is available for free online (through the Defense Technical Information Center (DTIC)'s Scientific and Technical Information Network (STINET)) , unlike the one discussed previously here. Written in 1967, this one is a very basic primer on scenario construction, discussing some of the details a designer needs to consider. The Peter DeLeon piece I described here is still my favorite single scenario design article, but this is a useful look at the process.
Two key concepts in this piece are credibility and relevance, and DeWeerd describes the tension that can arise between them when a game is intended to shed light on a specific research question. At times, it may be necessary to favor relevance to research objectives over scenario credibility, though DeWeerd recommends that in any such circumstances the designers make clear to participants what sacrifices in terms of credibility have been made.