What is the easiest way to do a mass update to leads, opportunites, etc.
I assumed that I could import an excel file with the information that I wasnt to update.  I tried to do that for my leads.  I created a file with FirstName and Name (the required fields) and 2 other columns for fields that I wanted to update.  Upon updating, however, I received an error message that the contact couldn't be updated because it already existed and I needed to make it unique and try again.
Is there another way to do a mss update or am I doing something wrong?