Most appliance will benefit from a simple wipe over with a damp cloth after use.
Washing machines due to the growth of bacteria caused by washing at lower temperatures will require extra attention.
If you live in a hard water area then regular de-scales will be needed. There are many de-scaler products available but soda crystals will suffice.
Simply pour a cup of soda crystal in the drum and put on a hot wash.
Also once a week make sure you are doing a hot wash, This will kill the bacteria growth and keep a smelling nice.