Instruct your staff on what you want them to say. You drastically reduce the chances or a positive impression when you let the phone ring more than 3 times. Avoid transferring calls when possible. Get the callers name, jot it down. Use the persons name during the conversation.
People like to hear their name.
When talking on the phone, imagine you're talking to a friend. Put aside your duties, really hear the person. Think like a customer. Seek-out their perceptions. Don't force your point of view.