(a) The earthing of an electric appliance is useful only if the fuse is in the live wire because in case the current in the circuit exceeds the rating of the fuse, it may melt and break the circuit first, before the current reaches the appliance.
It is unsafe to connect the fuse in the neutral wire because if due to some defect in the appliance an excessive current flows in the circuit, but appliance still remains connected to the high potential point of supply through the live wire. Now if a person touches the faulty appliance, he gets an electric shock because the person comes in direct contact of the mains through the live wire. Thus, it is highly unsafe to use fuse in the neutral wire.
(b) The metallic case of the appliance should be properly earthed.