When I'm looking for a single best thing, I'm usually looking for something about the person that's new information.  Questions in along the lines of "how did you get into your business" or "tell me about your last project".  There are usually details that are similar or different to my experiences (the same thing that creates referral connections for us).  Before I leave the meeting, I have the single best thing commited with a visual reference.  Nelson Carrasco (Painter on the Buckhead Team) and I had breakfast this week.  He told me a story about how he obtained funding for college.  It involved walking up to someone on a lawn mower - that's a picture that will stick with me.  Along with a great story about his determination.  If I have to refer to notes when I talking with a client - it's never going to produce results for my team members.