Listen first, speak second. Too many salespeople think their job is to share information, to tell the prospect every wonderful thing about the product or service. Nothing could be farther from the truth. When you ask questions and really listen to the answers you find out what their need is. Then, and only then, can you provide them with a solution to their problem. And that is what sales is all about.
Take a list of questions with you so you are sure to get the answers you need. And make sure those questions cover every aspect of a potential engagement with the prospect. Go beyond the specific need or project. Who are they as a person or company?