Recently I read Mark Shepard's Restoration Agriculture, in which he argues for replacing our current system of annual crops with tree crops. One of the interesting things about this book is what the restorative model can do for you, even if you are arguing from some false premises, versus the complete mess people make of everything when they use a revolutionary model- regardless of the soundness of their initial premises.
Anyway, Shepard and others have looked into what kind of ecological system most of America was in before modern agriculture. They found it was mostly an oak savanna. Within this system there were chestnuts, which are high in carbohydrates, and hazelnuts which have a good protein/fat content. In addition apples, grapes, various fruits would be grown. Perhaps most importantly- the thing that sells me on it, is pasturing animals through this system. I am not sure whether or not humans can change from wheat (or corn) to using chestnut flour or whatever- but I am quite sure we could mostly forgo the foods made from flour, feed pigs the chestnuts, and then have lovely bacon. I eat a paleo or ancestral health type diet, so I can see this working. I can also see that Mark Shepard appears to be making at least a little profit via farming.
So Restoration Agriculture would be a vital part of a new civilization engine.
Part two would be reading Christopher Alexander's work and trying to implement as much as possible this unfolding process rather than top down design. In his earlier books he talked of a pattern language, and I think this is crucial. I have heard him mention he thought all this would catch on rather quickly in the 70s, but that it didn't and in many cases he saw even people earnestly trying do it wrong. I believe this is because his metaphor of language is particularly apt, and whatever rudimentary knowledge we might have of it, we are not native speakers. It will take a few generations of sustained attempts at this sort of architecture to reach a point where people are fluent.
To reach part three, you need part one and two up and running well enough so that you can provide other people with a hotel environment. This means a high level of guest care, but not the ghastly sort of things that hotels do nowadays, like florescent lights, harsh cleaning chemicals and other foolishness. Here is an example: Perfect Health Retreat. Paul Jaminet noticed that the tons of writing he's done about health isn't enough, so he started a retreat, in large part because health includes a lot more than just diet.
So, part three is being able to host people and have them experience a lifestyle that is not yet available to most people yet. From an evolutionary perspective, the key aspect of this environment is that the modern disease promoters are absent, good nutrition is present, and a decent re-connection to light cycles is established. This will make anyone better, and, assuming the guest is smart enough, will lead to them making progress on the intellectual front- obviously one of the purposes of providing a hotel environment like this is so that people can listen and absorb new information.
Another aspect of this hotel environment, which is perhaps part four, is the ease with which a guest, upon deciding he would prefer to remain, and finding he has the capacity to do so, can. This is how the the civilization inches forward. There is a certain number of people necessary to farming and running a hotel, it is transitions and rapid increases or declines in populations that are shocks. So, what we would want is a slow transformation of the space in which the first hotel environment is from hotel environment into permanent residency- and at some point a new hotel environment would be built. At all times there should be some attempt made at calculating how many people the overall system can handle.
So this becomes an unfolding process itself limited largely by how many people have the sort of livelihoods where they can move to the new system.
Eventually, city-level densities could be achieved, but needless to say, it isn't easy (or possible) to hold those levels of complexity in my mind. One of the things I have thought about, though, is how children learn and what that might look like at some stage in the process. I am a proponent of unschooling. I also think Montessori has made some very salient points about what sort of things children are going to need and at what age. She believed young teens needed agricultural type work, due largely to puberty and the massive hormonal and emotional changes that occur during this time.
So, at a certain level of population, we'd likely large number of youth participating in precisely the sort of activities that help them learn the patterns of the new system. The pattern language of the new agriculture- and any new buildings that need to be built, would be taught during the middle school/early high school years. Further specialization might occur afterward, but I suspect most would want to participate and peer pressure would likely encourage the rest. This is where the future of the civilization gets locked down- especially if the youth find family formation as a result of commanding these skills to be rather easy. If the older generations are smart, they'd make sure it was easy. The key to keeping any sort of inter-generational group alive is to make sure the next generation develops their primary relationships within it.