To begin with I would not develop one policy. The reason for this is that in this era of democracy every party needs to feel that their needs are being met and not ignored. With that I would develop a series of policies that would cover all the bases of an eco-friendly and sustainable planet, or at least state. I would not target the nation because it would be harder to get the policy approved and implemented. With a state localized policy hopefully national news would hear about the policy and the idea would be contagious, such as CFL lightbulbs.
The first of a series of policies that I would develop would focus on waste. To begin I would try to get rid of all non bio-degradable products and implement a system where non-food products would have to be composed of a certain percent of recycled material. This would force major corporations to urge people to recycle their products so that the company would avoid a heavy tax. Money motivates everyone and the quickest, yet hardest way to motivate major companies to be more sustainable is by implementing an economic penalty.
The other policies I would try to implement would focus on the community such as community gardens and a community compost collection areas. This would encourage people to grow food locally and thus, cutting off the dependency of large corporations. Communal support is the direction that the nation needs to turn to in order for us to fix the damage we have done to the Earth and local policies will start this bigger change.