From Indiana U: 

Cases are narratives, situations, select data samplings, or statements that present unresolved and provocative issues, situations, or questions. As a teaching/learning tool, cases challenge participants to analyze, critique, make judgments, speculate and express reasoned opinions. Above all, although information can be real or invented, a case must be realistic and believable. The information included must be rich enough to make the situation credible, but not so complete as to close off discussion or exploration. Cases can be short for brief classroom discussions, or long and elaborate for semester-long projects. Cases are important for bringing real world problems into a classroom or a workshop— they ensure active participation and may lead to innovative solutions to problems.

Groups that are created for in-class discussion can be easily organized around the following four-person model. Each member of the group plays a specific role that supports the team's collaborative effort. These roles include:

• Leader: Responsible keeping the group on task, maintaining the schedule (meetings, deadlines), and maintaining contact information (phone numbers, emails).
• Encourager: Encourages conversation and inclusion of all opinions, and guides the discussion towards consensus.
• Prober: Ensures that the assumptions are correct and that there is sufficient evidence for the solution.
• Recorder: Writes down the group's solution that will be submitted for the group grade.

Cases can be more or less "directed" by the kinds of questions asked— these kinds of questions can be appended to any case, or could be a handout for participants unfamiliar with case studies on how to approach one.

• What is the situation— what do you actually know about it from reading the case? (Distinguishes between fact and assumptions— critical understanding)
• What issues are at stake? (Opportunity for linking to theoretical readings)
• What questions do you have— what information do you still need? Where/how could you find it?
• What problem(s) need to be solved? (Opportunity to discuss communication versus conflict, gaps between assumptions, sides of the argument)
• What are all the possible options? What are the pros/cons of each option?
• What are the underlying assumptions for [person X] in the case— where do you see them?
• What criteria should you use when choosing an option? What does that mean about your assumptions?

Managing discussion and debate effectively:

• Delay the problem-solving part until the rest of the discussion has had time to develop. Start with expository questions to clarify the facts, then move to analysis, and finally to evaluation, judgment, and recommendations.
• Shift points of view: "Now that we've seen it from [W's] standpoint, what's happening here from [Y's] standpoint?" What evidence would support Y's position? What are the dynamics between the two positions?
• Shift levels of abstraction: if the answer to the question above is "It's just a bad situation for her," quotations help: When [Y] says "_____," what are her assumptions? Or seek more concrete explanations: Why does she hold this point of view?"
• Ask for benefits/disadvantages of a position; for all sides.
• Shift time frame— not just to "What's next?" but also to "How could this situation have been different?" What could have been done earlier to head off this conflict and turn it into a productive conversation? Is it too late to fix this? What are possible leverage points for a more productive discussion? What good can come of the existing situation?
• Shift to another context: We see how a person who thinks X would see the situation. How would a person who thinks Y see it? We see what happened in the Johannesburg news, how could this be handled in [your town/province]? How might [insert person, organization] address this problem?
• Follow-up questions: "What do you mean by ___?" Or, "Could you clarify what you said about ___?" (even if it was a pretty clear statement— this gives students time for thinking, developing different views, and exploration in more depth). Or "How would you square that observation with what [name of person] pointed out?"
• Point out and acknowledge differences in discussion— "that's an interesting difference from what Sam just said, Sarah. Let's look at where the differences lie." (let sides clarify their points before moving on).

From U of Melbourne: 

A case is a story based on "real world" or actual events told with a definite educational purpose in mind. A case is a way of bringing the real world into a classroom so that students can "practice" on actual or realistic issues and incidences under the guidance of the teacher. Case-based teaching, unlike conventional topic-based lecturing and tutoring, is discussion-based and experiential in nature. The case replaces the lecture as the vehicle for learning, and the basis for discussion, exchange of ideas, knowledge, and experience among participants (Lynn, 1996; Rangan, 1995). The case study method has been popularized by the Harvard Business School and Harvard University's John F. Kennedy School of Government.

The art of running an effective case-study method is the selection of teaching cases so that learners are able to get from these case studies, understanding of issues and constructs that can be applied in other novel situations.

An excellent page of links at USC:  links

From Virginia Tech: 

Case-based teaching is a flexible model. If an instructor uses leading questions to direct students toward a moral or process he or she deems "correct," the model is not far removed from direct instruction. If the instructor, however, allows students to formulate their own opinions of a case by promoting group-coordinated research activities, debate, or simulated decision making, the model is more closely aligned with social constructivism. The key difference is the extent to which an instructor directly leads the student versus promoting activities through which students can lead themselves and develop valuable reasoning skill in the process.

Cases can either be "presented" to the student with one common ending, or "explored" by the student with different outcomes resulting from student choices while engaged with the interactive case. "Presented" cases can take many forms from simple print-based stories, to web pages with graphics and imagery, to full-blown multimedia with audio and video. "Explored" cases are more difficult to develop and require knowledge of interactive branching techniques. Such cases can be created by multimedia authoring programs (e.g., Macromedia Director), or through emerging web technologies (e.g., Macromedia Flash and Coursebuilder).

Related technique "problem-based learning" page at USC Dental: 

• What is PBL? Is it a new methodology? PBL is not a new model of instruction. Plato and Socrates required that their students think, retrieve information for themselves, search for new ideas and debate them in a scholarly environment. However, this process differs from the teacher-dominated approach used in most educational settings.
• Where did PBL come from? PBL was officially adopted as a pedagogical approach in 1968 at McMaster University, a Canadian medical school. (Neufeld & Barrows, 1974), because students were unable to apply their substantial amount of basic scientific knowledge to clinical situations.
• How Does it Work? Students in small groups investigate and analyze problems/scenarios. Using an organizer process of; 1) identifying the FACTS in the problem/scenario; 2) generating (un-criticized) their IDEAS about the scenario/problem and identifying just "what is the problem?"; 3) finally identifying the things they have to LEARN about - in order to test their hypotheses (ideas).
• Why is this an effective approach? The use of this three step inquiry-organizer helps students become familiar with a scientist's reasoning process, to fill the gaps in their own knowledge base, and to use their newly acquired knowledge to refine or discard their ideas thus generating a whole new set of LEARNING NEEDS. This model has been successfully applied to science instruction at all grade levels.

How do I safeguard the integrity of the process? The integrity of the process depends to a great extent on the groups themselves. Groups are kept small, approximately 5 students and a facilitator. At the beginning of the process, group norms are set by the students in the group. Norms include but are not limited to: Respect for everyone's ideas — no idea is "stupid"; not interrupting someone else while they are speaking; in other words "what should be OK in this process and what should not be OK — the rules of the game".

IDEAS are organized and then "rephrased" into a "testable" form (hypothesis). At this point the "problem" is also identified. The next step is to generate LEARNING NEEDS (what we need to know) that are prioritized and then divided among the group participants for investigation. Each group member researches their part and the next day the group meets to discuss and share the new information. This process generates a refinement of the prior ideas/hypotheses and generates a new set of learning needs. Assessments are given to the individuals in the group and the resulting grades are NOT for the group as a whole - the sharing of information becomes an imperative and because of this the group becomes a powerful force for mutual dissemination.