***Note on this process*** If you are generating diagrams from versioned data, you will likely not want to use joins as mentioned above. Joins don't take into account the version of the data that the diagram is generated from, it always uses default. So the values returned may be incorrect if you have changed the values in your version since it will always return what is in default. In versioned cases, don't use the joins. Instead, edit your schematic dataset and just add schematic attributes that point to the fields from the gis data (associated field attribute). This copies the data from the 'real' feature to the schematic feature during generation and update. Now for labeling and symbology, instead of a join, it is just directly accessible as a field and the schematic feature class. This actually has better performance as well for large diagrams. Follow the same steps above for saving the layer file and importing as the new default for that diagram template.