I guess it depends on what kinds of services you offer and how much your customers usually spend on them. If the spend $500 on average, you'd be spending a lot of time gathering info that would return you little. If they spent $.5M on you, then you'd do well to know what kind of food their dog eats. Well, not really, but you get the idea.
But I don't know if I'd start asking for all kinds of personal info on the first meeting - customer might think your intentions are less than honorable.
Beyond that, we keep the usual customer info like 1MT on file.