For small/medium scale Salesforce implementations (setups), good system design is kind of like measuring a customer for a suit off the rack, then handing it off to your tailor to give it the right fit.
You cannot successfully implement (setup) Salesforce until you create an effective system design.
And you cannot create an effective system design unless you perform effective business discovery.
However, at the implementation prices small and medium businesses can afford, you can only spend so much time performing business discovery. The budget is tight, and your customer has only so much time to contribute vital information to the process.
So, how do you manage this precious time?