I've mentioned before that one of the best ways of understanding the market for your product is to conduct one-on-one interviews with prospective customers. How a product manager facilitates this discussion is critical to obtaining useful information.
One reason facilitation is so important is that prospects often want to give you advice or tell you what the market wants. The purpose of an interview, however, is to understand what the prospect needs, not to find out what the prospect believes the market wants. So one aspect of facilitation is steering the discussion so that the prospect tells you about her situation and the problems she faces. A prospect is an expert on her situation and problems, not other people's situations and problems.