Based on my wacky belief that the best way to sell more wine is to get people talking about your wine, I point you to Guy Kawasaki's book preview of Andy Sernovitz's Word of Mouth Marketing: How Smart Companies Get People Talking.
The most powerful word-of-mouth advocates might be the customers who have only done business with you once so far. They are the most excited; repeat customers are probably accustomed to the great product/service and therefore, ironically, less likely to talk about it.
For example, one of the best winery tours used to be, maybe still is, at Sonoma-Cutrer. I learned a huge amount about how Brice Jones and friends were engaged in trying to make the very best Chardonnay (now trying something similar with Pinot Noir at Emeritus Vineyards). I would always recommend that people make an appointment and take the tour.
Guy's post gives some thought-starting examples of ways in which companies generate that all-important buzz.