Good negotiators should always think about how they can show the proposal they're making is fair to both parties,” Korobkin says. “Fairness” does not have one exact definition, but social psychology studies suggest that an offer people consider fair is one that is similar to what other people in the same situation are getting, consistent with market prices or terms, or on par with a similar transaction you have made in the past. “If the deal is fair,” he adds, “the person you're negotiating with never has to feel like they're being taken advantage of, and it'll make it easier for him to say yes.