So, are you advocating that we all "turn Ted Kaczynski", growing our own food and crapping in our garden for fertilizer and living in a hut by candlelight? Can't say I like your vision much, even if we ignore the practical limitations of population density.
Not at all, much less is required of us. In fact very little is required to half an average persons (MA) consumption.
Take the car to go shopping when the store is in walking distance? don't
Keep TV on while eating or staying in another room? don't
Drive kids everywhere, when they could take bike or walk ? don't
Buying lots of unecesarry things you don't need? don't
Keep on lights when it is not necesarry or you are not in the room? don't
Keep on heat when you could wear more clothes? don't
Leave stuff in power save mode instead of powering off? don't
Use cloths dryer to dry clothes which would be just as dry hanging for a day or two? don't
Run the washing machine with just a few pair of clothes? don't
Watch a lot of TV or play computer games divide that time by two and spend talking togheter as a family go out jogging another even eco friendlier hobby than watching TV.
Take bike public transportation, or walk whenever you can instead of taking car.
Go to vacation on a location nearer to your home, that is almost as nice as going across the entire world.
All most people need to do to half their (MA) consumption is to think about not wasting needlessly, and a minimal change to their life style. A very small cost to pay to save our earth. Combined with a less optimistic idea than PJ's 10, 20, 30 years to half our (MA) consumption by technology, that's it, and people in developing countries could live better too.