One of the most interesting parts of the book is that it claims you should "never criticize" another person. It says that every person can always justify their actions in their own mind and all criticism is taken negatively. As an example, even mass murderers have been interviewed justifying their actions. I tend to agree with this philosophy.

More specific than that: see things from the other person's point of view.

I'd summurise as "Trust. Be friendly. Take genuine concern for your clients point of view." These are pre-requisites for "win-win" situations.

I haven't read the whole thing, but another major point in the book is to subtly mimic the other person's body language.