It wouldn't be the wine industry without the Yin and Yang of buying and selling winegrapes: One side always wants less, the other more. But the real secret to a successful buying and selling deal is that both parties have to negotiate in good faith in order to reach an agreement on quality, price, contract terms and other conditions. But like any transaction affected and driven by market conditions, a supply and demand situation that is out of balance affects how one negotiates. An oversup...