It starts with ethics, because it is a design science founded on ethics. They are simple and three-fold:
Care for people
Care for the earth
Return the surplus
The first two are probably self-explanatory. Leave people and the earth better off when we interact with them; consider the impact of our actions. In other words, do no harm! Even more, with good design we can improve our relationships, our air and water, our soil fertility, our neighborhoods and cities, and our resilience in the face of whatever comes our way.
Return the surplus. Nature is abundant, people are generous. The benefits we receive when we work or build or plant or even create artistically, can benefit others just as they improve our own lives.
Next post: the principles of permaculture which guide design, in order to fulfill the ethics.