Ten Rules for Negotiators (from Naked Diplomacy: Power and Statecraft in the Digital Age)

1. Know your interests, your opponent and your brief.
2. Find the common vision, and make the parties own it.
3. Build alliances.
4. Make the right concessions, at the right time.
5. Understand the rhythm of the negotiation, and the interplay between public and private.
6. Shape expectations. Mitchell: negotiations are “700 days of failure and one day of success.” 
7. Manage your emotions. British Prime Minister Lloyd George to Sir Ronald Storr, his envoy in Palestine: "if either side stops complaining to me, you'll be dismissed.” 
8. Create incentives for politics. “It is never wise to gain by battle what may be gained through bloodless negotiations” (Attila the Hun).
9. Know when to walk away.
10. Ignore rules 1-9 when necessary. Unofficial motto of the United Nations: "Blessed are the peacemakers, for they shall take flak from both sides.”