Trouble is Neil has said much of what I would have.
Actually, that's not a problem - it's a great thing that so many of us are converging around similar conclusions: Seth Godin, David Armano, Mark Earls, Jackie Danicki, Alan Moore, Euan Semple and seminally Doc Searls and the rest of the Cluetrain gang, to name but a few...
So yes I'll agree with Neil, once again, that human interactions are critical. (Image by dotbenjamin via flickr)
They are exemplified in notions such as P2PR, Lean-Too Marketing, The Intention Economy (which Doc was referring to more than two years ago, so I'm a late comer on that!) and summed up as best as I know how in this slidedeck:
Adapting Brands To The Networked World
If you want a case study; try this. The slidedeck above also refers to some great examples of the use of social media.
Quick guide? Well I wrote this for 'how to blog'. Seems much of it is appropriate to all social media.
Time to tag: I nominate: Neville, Christopher, David, Mark and Jonathan
Dan was already tagged by Neil! This meme was started by Mitch.