Most of the literature suggests that the starting point should be "Receiving Material from Supplier" and I don't disagree with this.  There might be instances when you don't want to go back that far for a product VSM.  I facilitated a VSM team for a steel making company here in Cleveland and we didn't start with "ore being loaded off ship".  In fact, we started within the plant itself, starting at steel producing and ending at the hot band.  There are steps before and after this but that's the VSM map we wanted to focus on. 

Even in the case where we say, "Start as far back as possible," is the first step in the VSM "Delivery of raw material"?  Is it "Raw Material is Ordered"? (After all, material can't be delivered until it's ordered, right?)  Is it "Forecast is developed"?  (After all we don't order material just to order it?  We base orders on some sort of forecast, right?)  Is it "Customer orders product"?  (This would be more important in job shop environments.  In many of those cases, forecasts are based on what customers have actually ordered.)

Administrative VSM's can be even more challenging in picking the starting point. 

The best approach is to develop several options and talk about them.  Out of the discussion will come agreement as to the best starting point.  In general, farther back is better but listen to the team and hear where the energy is.