During the uncertain, early stages of a product design project, I've found the AEIOU framework very useful. It helps you see what the basic elements of a system are and how they interact. It gives you a map of the terrain.
AEIOU stands for Activities, Environments, Interactions, Objects and Users. To use the framework, you take the information you currently have about the project and try to work out which Activities, Envirs… etc are at play.
Here are the questions I ask for each—
Activities – what are people trying to accomplish? Consider this at as many levels as possible. What is the underlying sense of progress they're trying to achieve? What are they trying to achieve in the context of this tiny piece of UI?
Environments – what constraints are acting upon the elements of this system? Is the user in a hurry? What's their internet connection going to be like?
Interactions – which objects will the user need to interact with in order to complete the activity?
Objects – what are the digital items that the user is going to need to interact with? What are the different states they can take?
Users – which people share the activities you identified earlier? These are your users.