I listened to Getting to Yes by William Ury who is probably the most recognized negotiations expert few months ago.
If you never heard about William Ury, short TED talk might be the best way to get to know about his impressive career:
And here are the notes that I wrote down while reading it. Probably they will be of some use for you as well:
1. Always set a goal of negotiation form the very beginning: “You want to sell at the higher price and I want to buy at the lower price. Let’s find the fair price that can both agree upon.”
2. Always try to understand interests behind a position. How did you arrive at that price? Why do you consider it just?
3. Always repeat the position of another side: “Correct me if I’m wrong. Do I understand correctly that you consider this price to be just because…”
4. Always set a principle, external standard to judge the agreement. E.g. fair solution.
5. Separate a person from a problem. “We are very grateful for everything you did for us but it’s very important for us to arrive at the fair solution.”