The answers seem simple enough:
1. small communities (neighborhoods, villages, towns) Think New Hampshire-esque where decisions are always made at the local level not just by elected officials, but the real input and vote of the people. This must trump national input on all things but those that are truly international, e.g., treaties, war powers, etc.
2. Localization. This must be undertaken by the locals themselves. It can only succeed this way given the base must be as in 1. (Examples: the video.) People must lead their municipalities in this direction to show them what is possible. However, if municipalities do not devolve much power back to the neighborhoodish level, this too will fail.
3. Reduce, Re-use, Recycle.
4. In the US, you are literally looking at a Constitutional Convention to more clearly elucidate the division of power and specify local powers from State and state powers.
5. Capitalism must die. It must be replaced with something closer to the barter system and usury, of any kind, made, again, illegal. Usury leads to inflation and never-ending growth at speeds we cannot adapt to in a healthy fashion. Imagine how different a world this might be had banking, and more so, the fractional reserve system, not been created. Imagine how different it might be had population taken eons to rise to current levels instead of decades.
None of this is going to end greed, of course. That is why communities that are tight knit and strong at their core must exist: to stand against individual evil without stifling individual expression and production.
If, at the very least, usury is not removed from the equation, none of this is truly sustainable. We will, regardless of the systems adopted or adapted to, go through he same cycle in the future. Perhaps a simple way to put is this: we should strive to live in such a way that the only cycles of destruction we experience are natural ones. Cycles are real and inexorable. But I think we have some choice as to which types of cycles we submit ourselves to.
6. As alluded to above, we must choose harmony with our environment. Cuba provides a surprising example how this transition can start, though given the totalitarian model there, it might not be so easy in non-totalitarian nations.
The devil is in the details of implementation. In some ways, this may take care of itself. That is, if TSHTF resulting in TEOTWAWKI, those places prepared will prevail and their standard may become the de facto standard for that area or region. So the question applies only if we don't fall to the worst case scenario.
Let's say we end up with an extended recession, i.e. depression. This will leave the powers that be (TPTB) intact and lead to a long fight to realign socio-economico-geopolitically. In this case, small localization groups/transition towns will have to go toe-to-toe with TPTB. This will lead to conflict. That conflict might well be, and ideally would be, civil disobedience leading to redress and realignment. However, governments being what they are and human nature being addicted to power as it far too often is, more likely you would be looking at the imposition of military/paramilitary power to impose the current paradigms into the future. Again, the people would have the choice of open rebellion or the long-suffering, Ghandi-style rebellion. Not sure which Jefferson had in mind when he said a little rebellion is good for a nation.
None of this is going to happen without conflict if things get rough. In some ways, the worst that could happen for Freedom and The Pursuit of Happiness is for the S to not HTF. That's not advocating any open rebellion, but is a recognition of inertia. If the inertia doesn't get a shove, things will remain the same or completely collapse. Remaining the same, however, actually means get much worse as we drift further and further into a drone-like state of living. (Once again, Sci-Fi provides the vision of what is coming...)
Given what the population of the US has faced the last seven years, our shearing is nearly complete. Indeed, where are the protests? Where is the national strike? Where is th impeachment? 1776 is too distant. The Founding Father's voices muted, even considered quaint. Given this reality, how can anything happen except at the very local level? Yes, that is where it is starting, and where it must start - and end.
My vision is of a world that remains connected regardless of how good or bad the future becomes. The internet and other forms of mass communication must remain intact and must be a high priority for any and all groups of whatever size. Knowledge and information must remain available for those that need it. Communication must remain open to allow coordination and sharing of ideas, developments over time, etc. But, our day-to-day lives will almost certainly have to become far more pastoral. This does not mean science and advancement should not exist, but that it should be applied to making our lives healthier and happier in the holistic sense, not in the now-bankrupt idea of acquisitiveness. I envision a hobbiton-esque community with a gleaming understructure of hi technology. Smart houses based on renewable energies, mass transit except where impracticable, etc.
No matter how you slice it, to get to a sustainable world, not just a sustainable local community, we are looking at a shift in scale equal to the great changes of the past, e.g. The Dark Ages. With a great deal of luck founded in a great awakening, this might be The Light Ages.