Actually, one useful approach might be to observe/ask/question about what they *currently* do, how they do it, why they need to do it, and so forth. You can get into trouble a lot with a "This is how we've always done it" mentality(*), but it can also give you useful information about things they need on their web system.

(*) Been there, done that, "We run off X reports because we need then", "this is the accounting structure we need" (even though it's an old moldy pre-current government regulation structure they have to convert into reports they sent to the state government) and so forth.