Good negotiators aren't shy about staking out positions that are non-negotiable.

I know that we're supposed to keep everything open in a negotiation until the final settlement is reached, but posturing and positioning can dramatically impact that final result.

Let's agree to one thing - negotiating is all about sending messages. 

• If we send a vulnerablity message, our opponent will see weakness and move to exploit it. 
• If we send a firm resolve to stick to a position, our opponent will probably move on to other issues and recognize that there will be no concession forthcoming.

Example: You're in the middle of a negotiation to secure a client and seek a full commission.  The prospective client shares that they'd like you to reduce your commission one percent to match what a competitor said they'd work for.

Wow, what a great time to 'just say no'?

Now how you say it and how badly the client wants you and your services will greatly impact the final result, but, showing any vulnerability at this point is simply a failed strategy.  Instead, greet that 1% comission concession request with a pained look (flinch) and respond softly with, "I can't do that.  Reducing my fee is simply unacceptable."

You'd probably want to immediately follow that with a brief justification, such as:

"As I shared earlier, I'm a full service full commission broker.  Nobody works harder to market and service your account than I do.  But I can't reduce my fee."

Saying 'No' can be accomplished in many forms.  "I can't", "That's unacceptable", "There's no way I could agree to that" name a few.  Adopt those that fit you and your style.

Now be open to a trade off whereby our opponents later on agree to a concession that would be of value to us at which time we'd reconsider modifying what was clearly communicated as a firm position.

Bottomline, in a negotiating we can always move from 'firm to flexible'.  It's almost impossible to move from 'flexible to firm'....it just doesn't flow that way.  So be perpared to JUST SAY NO at strategic times to send the right message and to maintain your ranking as a good negotiator.