From Hugh Black's book Friendship, a few ways to cultivate friendship:
Attention to detail is the secret of success in every sphere of life, and little kindnesses, little acts of considerateness, little appreciations, little confidences, are all that most of us are called on to perform, but they are all that are needed to keep a friendship sweet. Such thoughtfulness keeps our sentiment in evidence to both parties. If we never show our kind feeling, what guarantee has our friend, or even ourself, that it exists? Faithfulness in deed is the outward result of constancy of soul, which is the rarest, and the greatness, of virtues. If there has come to us the miracle of friendship, if there is a soul to which our soul has been drawn, it is surely worth while being loyal and true. Through the little occasions for helpfulness, we are training for the great trial, if it should ever come, when the fabric of friendship will be tested to the very foundation. The culture of friendship, and its abiding worth, never found nobler expression than in the beautiful proverb, “A friend loveth at all times, and is a brother born for adversity."