How to develop a common schema for data exchange

I'm working with humanitarian organizations that do a lot of data collection in the field.  There is a tremendous amount of redundancy of data collection (surveys etc.) across different organizations and units because they don't have common data standards.  I would like to help them create a shared schema for common data such as nutrition and health data.  I would be grateful if anyone has any advice or can direct me to resources that describe how to go about this.  Intuitively I imagine that there is a process whereby a user group is formed to develop an agreed set of schema definitions for the data.  Some advice on how to design these schema definitions would be great. 

Thanks,

Fraser