A few ideas about Negotiation
paultyma.blogspot.com
paultyma.blogspot.com
You Can Negotiate anything is a short book that gives tips and pointers and gives examples of negotiating tactics.
Influence is a fascinating book by a psychologist that supports every major point by describing various psychological findings and major events that exemplify that point.
The first book is more of a how-to book and the second is more of a why-it's-the-case book. I found both to be valuable in helping me recognize negotiating tactics, which hopefully makes me less vulnerable to being unconsciously influenced.
The rules of negotiation very much depend on the situation so I personally take "n-tips for negotiating" with a grain of salt.