Developing basic drawing skills enhances attention to detail, and provides students with a life long ability to visually express themselves.
My method is very simple: Basic elements of design are introduced step-by-step into fun, easy projects that build upon each other. By the time kids tackle complex subject matter, line, shape, value, form, texture are second nature. In the process, they learn to focus on detail and really look at their subject matter, to use their own creativity to interpret what they see, and to place their emphasis on the creative process.
Side note: I avoid 'prescriptive' methods which I believe are counter to creative development by only exercising limited areas of the brain. Instead of teaching kids individual interpretation and expression - prescriptive methods simply teach children how to follow instructions and copy the teachers design. Instead of emphasizing the process, prescriptive methods place high emphasis on the final product.
I believe it is extremely important to stimulate all areas of the brain, to empower the kids by celebrating their individual interpretation and expression, and to teach them that their creative success lies more in the process and less in the final product.