The core of NVC involves four main steps: (1) observing actions, (2) identifying and stating feelings, (3) identifying and stating the needs which cause these feelings (when they are either met or not met), and (4) clearly articulating requests for actions. These four steps can be performed both on oneself and the person one is communicating with. Though easy to understand, it's actually quite hard to put these techniques into practice, due to the power of our habitual ways of interacting with people. My attempts to use NVC in the classroom and in my personal life have been difficult, but still effective--even if the only effect is to get greater awareness of what I am feeling and needing when someone does something (which makes it less likely that I will react with anger, resentment, or a passive-aggressive behavior).
One of Rosenberg's claims is that while people's preferred strategies for meeting their needs often conflict, the needs themselves could all be fulfilled if only they were willing to use different strategies to meet those needs. Now, like much of the theory behind NVC, I don't believe this 100%; there are surely some cases in which genuine needs conflict, such as lifeboat scenarios where there is only enough food or water for one person to survive. But like the other defects in the theory of NVC, this point does little to undermine the effectiveness of the techniques of NVC, which are quite practical. In the vast majority of human conflicts, even those involving physical violence, everyone's needs could be met without violence (even if not everyone's preferred strategies could be met without violence--such as if one side seeks to satisfy its need for security by killing off every member of the opposing side).
Another defect in the theory behind NVC is Rosenberg's claim that humans are not inherently violent; violence, he maintains, is something against human nature which we learn through our culture or society. To the contrary, since violence has been a part of every human culture, and since rates of death by violence were higher in stone age hunter-gatherer societies than they are in today's society, it is arguable that human nature includes the propensity for physical violence, and that if anything culture is gradually shifting our behaviors to less physically violent forms. But this theoretical quibble seems to have no bearing on the effectiveness of the techniques of NVC. These are grounded in careful observation of people's behaviors, coupled with acts of interpretation which seek to clarify feelings and needs, and finally with the formulation of clear action requests that can move dialogue forward more effectively than vague or judgmental criticism and demands.
My friend Lynn Ackerson first told me about NVC several years ago, but it took me a while before I actually looked into it further. I was turned off in part by the corny terms and techniques used by Rosenberg to communicate his ideas. As shown in the picture above, Rosenberg frequently uses tattered hand puppets to convey his points about NVC. This technique would be utterly laughable except that Rosenberg does seem to be in on the joke. It's a way of getting attention and of clearly summarizing points; when the "jackal" puppet says something, we know he is giving an example of violent communication, even when it doesn't sound like it--such as when someone snivels and says "I'm sad because you hurt me". Rosenberg also occasionally sings God-awful songs on his guitar (many of which he wrote himself!).
All of this, together with the problematic theory behind NVC, should be overlooked when one is considering the effectiveness of the techniques themselves. They are the real deal, and have been field-tested by Rosenberg in the worst conditions imaginable--when talking to groups of Christians and Muslims in northern Nigeria, some of who had killed relatives of those on the other side; when talking to convicted murderers and rapists in prison; when dealing with one's own road rage while driving behind the slowest car in the world! Likewise, Rosenberg's original inspiration for NVC was his own brutal experience as a child in Detroit in the 1940s, where he witnessed terrible race riots immediately upon moving to the city (in which many people were killed right in his own neighborhood), to being repeatedly beaten at his school starting on the first day because of the fact that he was Jewish. Rosenberg may occasionally indulge in cheesy or hokey antics, and his theoretical speculation seems off the mark, but NVC itself is no joke and should be practiced by more people.