A lot of the times I receive a software system's requirements from our customers in a very unstructured format. It is usually a bunch of "product development" guys from the customer's who come up with these "proposed solutions" to the business problems they have. While they are the experts at the business domain, a lot of the times they don't have the solutions right.

This results in

• multiple versions of the same requirement
• mixing up of two requirements into one
• a few versions of the requirement later down the line, the requirements which were combined together get separated out again, each taking with it some of the new additions

How do you work with such requirements coming in and sort them out into proper use cases and before development begins? What tools can we use to track a particular requirement's history, from the first time it was conceived till the time it gets crystallized into a proper use case? Estimating work against requirements received in such a fashion is a nightmare which ends up in making mistakes in understanding the requirement correctly and estimating the effort against it correctly.

Any tips, tools, tricks to make this activity more manageable? I'm just trying to get some insights from someone more experienced than I am in requirements management and effort estimation.