Whether you leave a group when attending business events, finalising a deal or get a "no thanks, we don't need your goods or services" always leave others with a sweet tatse in the mouth. At events if you are with one person at an event offer to take them for a drink or introduce them to others rather than leaving them on their own.
Whenever you recive anything always acknowledge it be it an email, letter or fax. That way people know you have received it
And when you hear you have been unsuccessful at gaining new business or getting a new appointment always thank people for their time and wish them success.
Keep the door open for another time; you never know what might happen next and as we always say in business...things change.
People often don't rememeber what was said or done but they invaribaly remember how they felt about you at a later date. Let that feeling be a sweet tatse