A neutral good character does good for goodness' sake, not because he is directed to by law or by whim. Such a character will obey the law, or break it when he sees that it will serve a greater good. He isn't bound strongly to a social system or order. His need to help others and reduce suffering may take precedence over all else.
A doctor who treats both sides in a fight and somebody who feeds the starving in a war zone are both examples of neutral good characters.