A few months back I added my then live in girlfriend as fiancée on my policy, and they shifted her as the primary for my most expensive vehicle and put me as the primary for my next most expensive vehicle. My total premium dropped by about $150 for 6 months to insure the both of us.
I passed this info on to someone else and I sat with him on the computer, added his wife to his policy, shifted the driver/vehicle and his rate dropped about the same $150. Then we changed his occupation title to something in the same exact area and it dropped another $100.