The basic problem is that whether due to culture or nature we tend to approach transactions as zero sum games (aka distributive), ie if I get something you must lose something. Negotiation is about thinking in terms of widening the pie, ie creating a win-win for all (integrative). Even in situations where it can appear there is no win-win, there often is.
Want a better rate? determine the value of what you are bringing to your client, then price your service accordingly. If they balk, then you make your case based on your analysis.
The text we used in class is this:
I believe it is suitable for pretty much anyone who can read.