We can brainstorm ourselves or in groups.
Questions I have found useful to elicit variables include: - How will we know this system is working well? What will be different? - What will help this system to work well? What will help this system to flourish? What do we need to get right? - What will hinder this system working well? What could get in the way? - Who are the stakeholders? What do they want from this system? What does this system need from them to be successful?
The variables we discover this way are like pieces in a jigsaw puzzle. There will still be missing pieces we will create along the way...