Just found this nice article on the web which is about how to negotiate whether you are a buyer or a seller. Useful for site flippers and domainers.

Article: The Art of Negotiation | TylerCruz.com: An Internet Entrepreneur’s Journey


snippets
The majority of the great sales I get is because I’m stubborn and won’t move much on my price. This works even better when somebody has approached you with a price, as you know they are extremely interested in purchasing your site, and they don’t know that you actually want to sell it.
so while you may get a better deal by saying you have other higher offers when in fact you don’t for example, it’s just something I don’t do for moral and ethical reasons.
Choose a gameplan before the bartering and stick close to it, not ‘jumping’ around showing lack of confidence.