Introducing a new local currency after an event

[iaaems]

Having established that 'we' are a greedy bunch - how do you/we go about introducing a new local currency?
From where I stand what ever was used would have to have some kind of universal value - locally at least. It would also have to be fairly administered - by someone or a group who was/were universally trusted. That's as far as I get with this really. The solution may be staring me in the face but is hidden in full view!!(?)