When in doubt, do the opposite of what a salesperson would do.That's good advice, because in most cases acting like a "salesperson" is a great way to annoy a prospect. In fact, you should check your entire shtick to ensure that you don't sound and look like somebody that's in Sales.
Not that I'm against Sales!
However, like all professions, Sales has acquired a particular "voice" that's supposed to be "how a sales pro sounds." If you're not careful, you'll find yourself talking in the overly-glib, fakey-flakey "sales" voice, because you unconsciously consider it part of the identity as a sales professional.
Same thing with your appearance. There's a dressed-too-much-for-success look that screams "sales pro" and which, frankly, turns off many prospects.
Am I saying you should mumble all the time and dress like a clown? Of course not. But I do believe that you should distance yourself from the stereotypes, because those stereotypes work against you. They put the prospect on guard and create barriers to closing the deal.
Nowhere is that more true than when you're at a loss for what to do next. The big danger is that, when you're in doubt of what to do next, you'll trap to some "salesy" behavior, like giving a sales pitch or attempting some kind of rapport building.
In such cases, you're probably better off doing the opposite -- like ending the meeting prematurely or even openly questioning whether the prospect really needs your product. I know that sounds crazy, but if you TRULY don't know what to do, you're better off doing something completely off the wall than simply continuing to sell.