Get them to agree a complete specification/scope before you start work.
You can thrash that out at the meeting, but make sure it's all written down and signed off - all too often, a project will be kicked off based on a general description of requirements and at every progress update along the way, the end users (or whoever) will ask for more features and functionality. This can turn a straightforward project into an impossible, never-ending task.
Probably worth asking how the function is being handled at the moment - you might want to base some of your data structures (or at least the presentation in some forms) on hard copy documents or spreadsheets that they are currently using.
Who (individual or department) will 'own' the system when it is released? (who will be responsible for enforcing any data entry policies, etc.
Will all of the users be on board with the idea of changing to a new system (up to you if you ask that one, but be aware that releasing an application to a willing userbase is much simpler than to a reluctant group - because they will not care about using it properly, or may purposely try to break it)
What do they expect to put into the system (how much, and what kind of data)
What do they want out of the system (reports, analyses, exports)