If you want to really understand how social media/tools are changing how we work, play, activate change and live, pick up Clay Shirky’s Here Comes Everybody: The Power of Organizing Without Organizations. And if you are seriously considering communities as part of your marketing strategy, Do Not Pass Go without reading this.

Here are some of my takeaways:

There are three essential pieces of a community, starting with purpose:

1. Why: what’s the the promise of the group/community? Why would anyone want to join or contribute? “Creating a promise that enough people believe in is the basic requirement. The promise creates the basic desire to participate. ” Note: in my experience this is where marketers usually spend too little time. Or, rarely challenge their own. assumptions.

2. How: this is where you figure out which tools will help people do what the community is all about. Note: too many companies are buying tools and then trying to make a community fit the tools. A recipe for disaster — or, at a minimum, enormous frustration.

3. Rules of the road: this the what Shirky calls the bargain: “If you are interested in the promise and adopt the tools, what can you expect and what will be expected of you?”

People have always wanted to share and help one another. Pervasive, easy-to-use communications tools and ” the collapse of transaction costs makes it easier for people to get together — so much easier, in fact, that is changing the world.” “Social tools don’t create collective action — they merely remove the obstacles to it. This is why many of the significant changes are based not on the fanciest, newest bits of technology but on simple easy-to-use tools like email, mobile phones and websites, because those are the tools most people have access to and, critically, are comfortable using in their dauly lives.”

Incentives for participating are not financial: Attention, the desire to see your work spread, the desire to help others and be helped.

Why some communities grow and others don’t: “They grow if enough people care about them, and die if they don’t.” (This goes back to getting the promise right.)

How did you do that?: communities where a group of people help one another get better at some share task or interest — called communities of practice — are especially pervasive and appealing. The basic question that can trigger a community of practice: “How did you do that?”

Not everyone needs to be passionate, participate a lot: in the old model we had to work hard to get people passionate enough to act, because acting was a lot of work. Today you can have a handful of highly-motivated people participating a lot — and “people who care a little participate a little, while being effective in the aggregate.”

A small number needed to get things started: “The number of people who are willing to start something is smaller, much smaller, than the number of people who are willing to contribute once someone else starts something.” Tap into a small core of passionate people; don’t expect a lot of people to contribute at the get-go. Many are more comfortable adding to what someone else has started.