This is based on the concepts (like 'unfulfilled need' and 'ambition') and community framework from @alexknowshtml's Community Builder Masterclass.
Starting a community is like lighting a fire in the dark.
Initial stages - light the match
Wood is 'unfulfilled need' - burning wood releases energy in the fulfillment of the need. Community is the coming together to address shared needs; creating a stable, vibrant, resilient fire that not only fulfills the common need, but also propogates the fire and supports more burning.
You only start a fire when you think you can find wood that will burn well enough. You might not be able to see it clearly in the dark, before you start, but there's no use making a fire just because you want one - despite the fact that you've got no wood. Similarly, you may feel twigs that you're pretty sure will catch, but finding your hearth wood is more difficult. You won't know in advance exactly what core logs will sustain your fire. But you should have a hunch that they're out there!
You can't start a fire by holding a match to hardwood anyway. You need to find some kindling which will catch readily...
So in the early days, you need to spark the fire based on something you know will catch - your match might be a meetup event that you invite your friends to and put out the word to a couple of other community groups. People don't jump straight in to something they haven't really felt out, so a 'safe', 'fun' event is a great place to start. Get a couple of speakers as drawcards, some music and free stuff if you can.
This stage is all about the excitement, spark, and making important initial connections. It will be quite hands on - but it doesn't mean you should do it in isolation. Ideally, you'll connect with the interests of at least one other.
Nurturing - fan the kindling
You can strike the match, and you can light some kindling... but chances are (unless it's really potent stuff) that you'll need to put a lot of your own hot air in to fanning the kindling in the early stages. Kindling can die out even more quickly than it lights, so you need to be on top of it, continually fanning and prodding. You'll probably have a few different sorts of kindling, some that will burn quickly and easily but won't last (your paper might be themed parties), some that takes a bit more effort, will last longer, but in isolation doesn't produce a very strong flame (your splinters and twigs might be discussion events)... you need to monitor and manage all of these, in an effort to get a solid, active flame going that will catch more substantial wood. Don't dump a whole lot of fuel on the fire at once because it will snuff out what's there, and don't try catching solid logs too soon either because they just won't burn. You need to build it up gradually, and if you have a few different sorts of kindling (which is always wise), you'll need to feel out what works best and how different things burn.
In this stage, you'll be an active champion and responsive organiser. You'll be talking to people, connecting dots, organising, bringing things together... but you also need to be very responsive to changes, and use this time as an opportunity to understand what interests are out there, and what will catch. This phase will take a lot of your time and attention and be very fragile.
Grounding - identify the hearth logs
Burning kindling, sticks and smaller logs will give you the chance to test what sorts of things burn, and how they burn. You'll develop a better sense of the sorts of wood that burn best, and with the light of the fire you'll be able to guage what sort of fuel supplies are available. Use this testing and the new light to identify what wood will be the heart of your fire. This wood will be your ambition.
This isn't really a separate phase in time, but it does need to happen between getting the fire started and moving on to burning solid logs. This is your 'research', and the analysis of this research, turning it into something solid to work towards. It's best to do this with a growing group who can help nurture the fire in future.
Rally - direct energy at the logs
The happily burning twigs are the activity of the active, but immature, emergent community.
Direct attention towards the logs, by placing the sticks and smaller bits of wood around the logs. Split bits of hard wood off that will catch and help spread fire to bigger logs. If you've built the fire up properly, you won't need to pay much attention to the smaller stuff - you may need to dump more twigs on, but this should be easy enough if there is fuel nearby and it won't take too much of your own effort. But don't waste time admiring the glow of the small stuff! Sooner or later you WILL run out of readily available fuel, the fire will wane and you'll be back at point zero. You need to take advantage of the fire you have to move on to the more substantial and sustainable wood. This will catch slowly around the edges at first, it may seem like it will never really burn, but with some persistence you'll find the fire around it has done its work and the main log will catch.
Use campfire stories to illustrate the unfulfilled need that can form the heart of your community, its long-term fuel, and the potential for the community to address that need itself. Let the community activity fan out in different directions and burn strongly, to keep things going without too much fiddling, and to keep the heat up, but also direct attention and experiences back towards the centre - towards the core ambition and the future of addressing this. Splinters of hardwood can make good campfire stories of little ways that we can fulfill the ambition. But we also need to think about the future, and develop a shared sense of burning that future.
This phase is primarily about leadership. You shouldn't need to be actively organising or championing activity at this stage - perhaps just stepping in to prompt, guide or help sometimes - because if the community activity is built on a solid mix of fuel and a suitable volume of activity then other community members will look after this on their own. This leaves your attention to foster discuss and visioning of the community's future.
If you're still doing most of the organising at this stage, you need to find ways to better structure the twigs and sticks for mutually supporting community activity, and also find ways to step back and let the fire take on its own shape. If you're still very hands on, it is probably a sign that you've been too controlling and haven't fostered the emergence of natural community activity.
Structuring - build up the logs
Getting the hardwood burning is probably the hardest part. Once it's caught it burns quite a strong, long lasting flame. For this to form a resilient community fire, the wood just needs to be built into some sort of a structure. This might be little more than identifying a few suitable logs (initiatives, projects or programs for community activity in pursuit of the ambition) and throwing them together. Some fires might demand a bit more thought into how these logs are structured - particularly if there is a chill wind blowing or rain.
This phase is about creating resilient frameworks and structures, for the community activity of the hearth to be self-supporting, reinforcing, and vibrant. This means establishing imperatives, policies and organisational systems. While these can be initiated earlier to guide community activity, they can stifle the fire without the solid flames of burning hardwood.
In this phase, it should be possible to step back from championing and leading the vision, which can be adopted and carried on by the maturing community. The main firestarters' focus will be on internal matters of systems etc, and you're most likely to be working with the community's core team than with the broader community. There should be little need to put your own hot air into the fire, though you need to keep your eyes open to make sure the fire is progressing healthily.
Also bear in mind that this phase doesn't mean it's time to start directing and managing - structures created must be responsive to community energy and intention. There's no use building a beautiful monolithic pyre on top of a log, only to discover later on that the end sticking out the side of the pyre is where all the action is at, and it's starting to whither and die out due to its exposure.
Pre-maturity - participate
If the community has grown through all the past phases, then by this stage it will be active, energetic, resilient and long lasting. There will be little need to actively interfere with it. The main attention it needs is oversight and a bit of maintenance to keep it on track. Things to watch out for particularly are adverse external conditions, and the emergence of internal pathologies due to structural issues.
This stage is happy because it frees you to actually participate freely in the community, enjoy its warmth, in a way that probably hasn't been possible earlier on. In fact, active participation is the best way to keep on top of emerging issues. It's just important not to get complacent.
Post-maturity - steward
The hearth wood of a fire will eventually break down, structures will break down, and while the fire will remain active and fairly stable for some time, it will lose some of its energy and intensity as fuel is spent. The flame is still strong - in fact, the smouldering coals of a mature fire can be the most reliable and efficient source of energy. But volume decreases, and as structures collapse this has the potential to both release new energy, or smother more fragile activity.
Communities in this stage will need a little more attention, but it's probably time for hard questions. The first one will always be about the underlying ambition - with this no longer a stong imperative, what happens now? Communities can last, and often get very stale, on the basis of momentum, long past relevance to their purpose. This means careful selection of any new fuel, and also hard questions about what to let go of, to keep the community going with good vibrancy but in a new, different - likely smaller - role.
Where to from here? There is no set path.
Letting go and walking away is one good option.
Rebirth is another. This might mean finding new sources of fuel to dump on the fire, to hope it can be reborn again in a new form, rising like a phoenix from the ashes. Or it might mean taking the coals or flames from this fire to start another elsewhere.
In any case, it's best to be aware of the dwindling fire, and to be prepared sooner rather than later.