In his sales tactic talk, Troy Harrison discusses the two types of questions that sales people must ask.
A sales exchange is always rooted in the "quality of discovery." That is, you're attempting to discover the needs and wants of your client. Harrison argues that too many salespeople get encumbered by small picture questions. They fail to see the bigger picture, which is where a company is heading in terms of their management strategy and overall needs. Harrison emphasizes that if you only ask questions relating to your product or service, you will miss crucial information that will ultimately impact your understanding of the company's needs.
He finishes by introducing us to the "80% rule." The principal states that 80% of your chance to win a sale is determined by the time you ask your last question. If you ask more (and better) questions, your eventual presentation will be infinitely stronger because it addresses the company's direct needs.