If its genuine, it helps. If its forced, it looks fake and can come across as untrustworthy. But overall, a positive attitude bodes well in sales.

I broke a tooth and my smile is not winning :)

I find that, sometimes, a genuinely happy salesperson will incentive me to buy more.

For me, while I was/am always willing to meet face-to-face with clients, sometimes they are just too busy, and we have great telephone relationships. One of the most important things, IMHO, is humor, which in spoken-word is essentially a smile. I have a number of introductory phrases such as, "Oh, Fred Klein referred you? And you called anyway?" This always got a chuckle, and we moved on. My point being, whether it's a smile or a chuckle, a good sense of humor goes a long way.

As the saying goes, honey catches more flies than vinegar. In my many years in sales, we were trained to answer the phone with a smile. A good sense of humor always breaks the ice, as Bruce observes. And enthusiasm, sincerity and caring are essential.