If you were ruler for a day/week/month/year (your choice on the time) you would...
Oh, my! Please, get up off your knees. I am a benevolent dictator, not a tyrant.
Except when it comes to protecting our planet. If we kill that, then what will we do? I will have no subjects!
In order to continue my rule, we would need to make use of the most available power in every locale... sun for the south and wide open spaces, water turbines in places where rivers run, wind power where that is possible... and save the petroleum based power for areas with no resource and for emergency operations.
Mass transit would the norm rather than the exception. Small personal vehicles such as scooters and low power motorcycles and bicycles and feet would be the preferred modes of transportation. I was driving home from my uncle's house today and imagined the highway and the interstates with no cars. Trucks would operate locally, taking their loads off trains rather than running each load down the highway.
People would grow their own food as much as possible and trade with others. I haven't got a green thumb myself (thank goodness for the royal gardeners), but I could sew up some curtains or paint a room for you.
There would be very little trash. Everything would be composted if it were vegetable matter, or reused or recycled if it were not. It can be done! If you had told me this a few years ago, I would have laughed in your face, but now each Friday, we roll out a cart full of paper and plastic and glass to be recycled - and a cart with one bag of trash in it. One. I am amazed - and convinced that it is absolutely possible.
Rather than overrun our sewers with waste water, set up a separate system in every home to reuse greywater for gardens, so that we're only treating the waters that NEED it. Your bathwater could be quite beneficial to the veggies - and the soap will help deter pests.
As ruler, I will do everything in my power to make sure our planet has its "happily ever after."