I have been in the business for over 20 years! Professionalism and ones reputation can mean the acceptance of a contract or not, especially when you are going up against multiple offers. I am fortunate enough to have a positive reputation amongst my peers and business contacts and I can't tell you how much that has helped my clients in the past.
Negotiating is a skill that isn't always black and white. Sometimes price is the most important thing to a client, sometimes condition or flexibility to closing date (maybe a contingent offer needing a longer close date) ... regardless, know that I will work till I'm blue in the face to try and obtain the most I can in every facet of the transaction...especially what's MOST important to you! The skill is to do so without being pushy & aggressive. I love doing all this without the other side really even understanding what's happening until it's all over!