Typically, you would want to use one shared parameter file for a "firm", or at least for a single location/office. The best way is to create the shared parameters, get them into your template, and then each project started after that will have those parameters available. At least the the Architectural side shared parameters are required if the parameter is to appear in a tag, or the parameter has to be applied to more than one catagory of object, or to make them editable in a title block. This is NOT a rule, but an observation. Typically, the Architect will have to send their Shared parameters file along with the Architect's Title block, to enable a consultant to utilize the architect's titleblock correctly.
Scott Womack