Good negotiators follow just a few rules, and they make lots of use of a magic word. Usually, the rules and the magic word work fine. Even when they don't, however, they save much physical and emotional wear and tear. You can't negotiate unless you know your objective. Nevertheless, don't ask for earthshaking solutions to ordinary problems.
Realism is an important part of negotiation.
Once you know what you want, believe in it. Effective deal-making requires confidence that you're honestly entitled to what you are asking. Negotiations honorably done succeed and stand the test of time. Dishonesty kills negotiations and frequently packs everyone off to a courtroom. This amount is what you want, minus uncertainties of various kinds.