Tradition often passes on with it rules and rituals, which ideally are guidelines but which face the risk of becoming hard and fast. The challenge then for sumi-e is to maintain the roots while allowing individual expression, experimentation, and growth. For the artist, it means trying the untried, risking the safe way of doing things for the unknown way, pushing past what is comfortable, while holding onto the spirit and the essence of the subject. It depends on your style of learning. There are some great books out there that can walk you through basic strokes, techniques, and philosophies.
Many people do better with camaraderie and an instructor.
That way you can actually see how to paint, and you can compare your paintings with those of other people at your level. But teachers are not always available to everyone who wants to learn sumi-e. I'm a strong proponent of experimentation. Try it yourself, play around with the brush and ink and paper. You can learn how the ink and water react on the paper and how to load the brush with mulitple shades of black so that you can get many shades in one stroke.