You don't have to be gruff or combative to get your way in business. Sure, it works for some, but I'd take rational discussion over posturing any day.
It's been said that listening is the least expensive concession you can make. Don't interrupt. Concentrate. Empathize. "Seek first to understand, then to be understood," says author Stephen Covey. Ask questions that begin with "why." I'm amazed at how easy it can be to make a deal, once you find out what the other side wants. The reverse also holds. Your opponents are more likely to work with you if the reasons for your demands are clearly articulated.
When you do cut a great deal, don't rub the other side's nose in it, or brag so loudly that it gets back to them. Let them save face. If they need one, give them an excuse. Talk about how things have changed. Or point to some third-party standard of fairness. First-class negotiators get what they want and leave the other side feeling like a winner.
After you shake on it, you still want the other side to consider you someone they'd like to work with again. A challenging opponent of mine brought this point home at the end of a particularly torturous negotiation. When it was over, he stuck out his hand, smiled and said, "Closing is a beautiful thing." At first, I was stunned, but I had to admit he was right. Did this one remark make us best friends? Of course not. But it did clear the air, should we meet again.