Each prospect will have their own set of questions and concerns, but what I have found most valuable is to provide content in the form of books, videos, articles, podcasts etc. that answer a lot of their questions before they ever speak to you. This not only allows you more time to dig into any specifics they are really concerned about, it also means that they have a high level of trust in the work you are doing before you even speak. This alone can save you huge amounts of time.
Any time a prospect is unsure of something it is a great indicator to me that I need to produce a new piece of content to solve that.