A great article about the Alternative Futures at the Manoa School by Jim Dator, with clear instructions for facilitators on how to conduct a scenario workshop using the 'four generic futures' method:

Components of a Futures Visioning Process The necessary components of a futures visioning process are these, and in this order:

1. Appreciating the past: First is a discussion of a common understanding of the history of the community or group involved, going back “to the beginning” of the community or group if possible and not just the immediately-remembered past. It is not possible to think usefully and creatively about the future of anything until you understand its rationale for coming into existence, the many different facets of its past.
2. Understanding the present: Second is a discussion of the problems and possibilities of the present. Until people are able to vent their concerns and/or satisfactions with the present, they will often be unwilling and unable to think usefully about the future. They may resist futures activities as “pie in the sky” avoidance of urgent problems of the present unless allowed to vent. They should also understand that sometimes solutions to present problems lie “just ahead” over the horizon–to see “the future” as a reservoir of solutions (and new challenges!), and thus that it would be a mistake to try to solve current problems without first engaging in a complete futures process.
3. Forecasting aspects of the futures: Third is a discussion of possible challenges and opportunities from the futures (using as a default a roughly 20-50 year time horizon). It is absolutely essential that everyone have some sense of what is likely to be “new” about the future, as well as what aspects from the past and the present might or should be brought for- ward into the futures. What are the major continuing trends, novel emerging issues, and significant continuities from the past that will result in “the present at a later time” (aka, “the future”)? We often use the term “surfing tsunamis” to convey these interacting components of the future.
4. Experiencing alternative futures: Fourth, and the most crucial of all, is an experience in one or more of at least four alternative futures that are based upon different mixes of the trends, emerging issues, challenges and opportunities from the future, and also based upon different idea about how the world works. There is no single future “out there” to be predicted. There are many alternative futures to be anticipated and pre-experienced to some degree.
5. Envisioning the futures: Fifth is a futures visioning exercise in which participants now are better prepared to envision a preferred future for the community or group 20-50 years hence, based on the past, present, and alternative futures discussed previously. Visioning a preferred future is the main purpose of this entire exercise. But visioning should take place only after participants have become aware of what is new and what is old, and what challenges and opportunities lie ahead, in order to create one or more preferred futures for the community or group.
6. Creating the futures: Sixth is a discussion and decision of what to do now and in what sequence in order to begin moving the community/group towards the preferred future. Futures visioning is not just about imagining a preferred future. It is about using that vision to decide what to do now in the present in order to move towards the preferred future.
7. Institutionalizing futures research: One conclusion of that discussion and decision is of the necessity of setting up some kind of an ongoing 'futures' unit which can keep the future-oriented process going. This should include some kind of a “scanning process” which continues to “look ahead” for emerging challenges and opportunities in the immediate and more distant futures, in order to inform the community/group (and its leaders) about them. A related aspect is either to agree on a time in the future when this entire process will be undertaken again (eg., to agree to repeat the process if five years), or a way in which the futures participative process can begin again if the original vision is felt to be insufficient in the light of experience and/or information about new challenges and opportunities from the futures.

(…) One point of this entire exercise is to consider how to “succeed” in and enjoy whatever future you find yourself, by anticipating, preparing for, and moving affirmatively toward it. (…) I eventually decide that all of the many images of the future that exist in the world can be grouped into one of four generic piles–four alternative futures. Sometimes the futures might seem to overlap between two or more piles, but most seemed to fall very naturally into one of the four–and no more. None of these four futures is intend- ed to be any better, or any worse, than any other. They are all “positive” to those who prefer them, and they should be presented positively. These four futures are “generic” in the sense that varieties of specific images characteristic of them all share common theoretical, methodological and data bases which distinguish them from the bases of the other three futures, and yet each generic form has a myriad of specific variations reflective of their common basis. Also each of the alternatives has “good” and “bad” features. None should be considered as either a bad or a good future per se. (…) Four Generic Futures:

• Continued (economic) growth - business as usual
• Collapse (social, environmental…) - NOT the worst case scenario!
• Disciplined (society)- survival, conservation, fair distribution, fundamental values
• Transformational (society) - through technology, post-humanism, etc.

(…) Experiencing and Responding to an Alternative Future If possible, there should be four rooms, each decorated to depict one of the four alternative futures. In them are artifacts from the future, decorations, moving or static pictures, sounds, smells, and actors exemplifying life in each future. If it is not possible to decorate the rooms, then each room should have written copies of the one future that will be read and discussed. Either after “experiencing” their future directly, and/or after silently reading the description of their future, participants will sit in groups of no more than 10 people each, and discuss and jointly answer the questions according to the instructions. If it is not possible to have four separate rooms, then people should be assigned to small groups for each future within a common room, sufficiently separated from each other so that participants within each future can discuss their own future without hear- ing what others are saying. Note: All four futures should not be distributed to the participants beforehand. Each participant should initially only know about the future she will “experience”. Thus, organizers should hand out copies of only one future to each participant at each table. After the briefing session is completed, copies of all four futures should be made available to all participants. (…) the four futures exercise discussed above is intended to be part of an overall process that begins with examining the past and present of an organization or community, and is followed by a preferred futures visioning exercise which is itself followed by activities that use the alternative futures, and especially the preferred future, as the basis of a strategic planning process.