Know when to walk away. Developing and abiding by a system for negotiations is critical to getting what you want. This entry will only address a small portion of the overall negotiations system required. However, when negotiating you must be able to walk-away and take a break.
Remember, the following nemonic is great for helping you remember when to halt the proceedings and take a break. Stop if anyone is:
Get back together and continue only after you believe your side and the other side of the negotiation are no longer in a HALTS state.
[ Hat tip: Roe Goddard ]