Several years ago I read a book by world renowned sports agent, Bob Woolf titled Friendly Persuasion. The tenets of that book and the very simple markers that it taught me have given me confidence to approach most any conversation.
Here is one: Listen. Listen. Listen.
When I want to let the other side know my goals instead of making demands, I make suggestions, I make recommendations, and I make proposals. "May I suggest this?" is so much more graceful than "This is what I want." "Could you live with this?" "Does this make sense?" "Is this alright with you?" "Is this crazy?" are all preferable to "You better do this or else." If I have come to what is my final position, I will most likely say, "I hope you understand, this is the best I can do, I hope we will be able to work together."
Take stock in your voice and how you express yourself. A good negotiator uses a nice, low-keyed, pleasant voice to his/her best advantage. Speak slowly, clearly, it is your most important tool. Remember to have kindness in your voice. It is something that people respond to.
Listen. Listen. Listen. The best way to learn a person's positions, problems, traits, likes and dislikes is to listen intently.
Let them talk. They may reveal some information you may not have gotten if you had interrupted. Use silence as a strategy to plan your next move, not just time out between soliloquies. It is simply impossible to act sincerely interested in what somebody is saying or offering if you monopolize the conversation. Let your own silence speak for you occasionally.