Start with the operating workflow
Follow one complete task from its trigger to its outcome. Identify the users, records, handoffs and exceptions before deciding on the screens or technology.
Name the data owners
Document which system is the source of truth for every key record. Ask who may access data, how changes are handled and what must be retained.
Prioritise the first release
Choose a small end-to-end journey that solves a meaningful problem. This is more valuable than a large feature list that has not been tested with real users.
Check integration realities
Confirm supported APIs, permissions, documentation and failure handling. An integration should be observable and recoverable, not an invisible assumption.
Agree acceptance and ownership
Set measurable acceptance criteria, deployment responsibilities, source-code access, documentation and the post-launch support route.