I use on my cases studies the following structure:
1. Initiatives/Outcomes - this is what was done and is part of the put what matters first. I don't like to create mystery on case studies
2. Scenario description.: tell a story of what is happening, in a way that the reader can identify and relate
3. The Problem: Describe the what is wrong, or can be improved, or even is just not in sync with what the client wanted
4. The Solution: Describe the steps you took to assess the situation, proposed measures / remedies applied.
5. Outcome: described measurable impacts, preferably with hard numbers
6. Quote: get a quote from your client, with name and title
7. Contact request: give your name and contact for further information
NOTE: Whenever possible give credits to the team that was part of the case described with names and titles. And always ask for permission and approval when posting cases.