When I tackle a problem domain, I first frame out the space. To do this, I list out scenarios and sub-scenarios. I group the scenarios under categories. Sometimes categories come first, sometimes scenarios do. I call the result, a Scenario Frame.
I use Scenario Frames to evaluate platform, tools, and guidance. I also use them for product design, innovation, competitive assessments, subject matter expert reviews, arch and design reviews, and as a way to build shared understanding of a problem space.
Here's a Scenario Frame Example my team is creating to enumerate and evaluate Source Control scenarios in VSTS 2005:
What's your favorite tool for framing out problem spaces?