With an open diferential whichever wheel has less traction will spin. By chaining one front and one rear you'll have the opposite ones spinning.
Going uphill it is best to chain the rear (both sides) but if steering traction is going to be an issure the front would be better (in 4x4). The problem with chaining the front is the steeper your hill is the more weight transfers to the back, thereby decreasing front end traction. So just how steep is your driveway?
-Scott