In recommending Bargaining for Advantage: Negotiation Strategies for Reasonable People by G. Richard Shell; Negotiate to Win: The 21 Rules for Successful Negotiating by Jim Thomas; and, my favorite Beyond Reason by Fisher and Shapiro as the three Best Business Books [on] Negotiation to arrive on our commercial shore in 2006, reviewer Nikos Mourkogiannis  of Strategy + Business outlined the three essential elements of every negotiation -- art, science and wisdom.

We reprint an excerpt below and link to the full article above.  

E]very negotiation involves three fundamental elements: art, science, and wisdom.

Artistry is always involved, because negotiations can never be fully planned; the circumstances vary too much. At the heart of even the most mutually beneficial negotiation, there is always a haggle between two conflicting positions. A creative solution can clear a stalemate and produce agreement, but not by eliminating or resolving the conflict; rather, by suggesting new, acceptable concessions that make the conflict less intense. Making this happen is the art of negotiation.

The second element is science. Why would one person ever concede anything to another? Because the first person judges that without that concession, the second person will walk away from the deal. The leverage held by each of them can be determined analytically: It can be expressed as the difference between the expected cost of the concessions and the cost of a failure to reach agreement. The science of negotiation is the process of maximizing leverage — what strategists call advantage — by analyzing this difference in cost (which is subject to change at any moment).

The third fundamental element is wisdom. Every negotiation entails some wisdom. Otherwise, we would just have open conflict. Wisdom is the ability to observe the negotiation as it evolves, so that one can seize the opportune moment just as Prince William did. Wisdom also involves the ability to anticipate the negotiation’s most likely results after the deal is struck. A skilled and ruthless negotiator may win every last demand, but never again be invited to the table. A cultivated sense of timing helps any negotiator reach his or her most important goals: to win the most critical concessions, or possibly to negotiate a change in the rules that will provide winnings forever without any more negotiations being necessary.