Whenever calling or writing a patient, find out all you can about the person from a prior contact note. For instance, if the treatment chart has a notation saying the patient just had a baby, start the letter or conversation by saying: "Hi, Janet! Congratulations on your new baby! Did you have a boy or a girl?" Then gently go into the reason you're calling.
It's always more effective to start a conversation or letter in this fashion. This way the patient gets the feeling that he/she is not just a dollar sign to you and that you really do care about him/her. The patient will also be much more apt to pay you than if you just said, "You owe $100. Payment is past due!"