Unplug it and pull from the wall.
Remove all food and put in a cool place.
Take out shelves and drawers and wash in hot soapy water. Rinse and dry.
Wipe the interior including the roof with a clean cotton cloth rinsed out in hot water with a little washing-up liquid.
Run the cloth between the folds of the door seal – much grot lies there! – then wipe the outside.
Check the condenser coil at the back for clumps of dust – vacuum any away.
Reconnect fridge, push back, return shelves, drawers and food.