Keep it cool but not too cool..

“Don’t let your fridge use too much energy by keeping it colder than it needs to be. If it has a thermostat, set it at 38o Fahrenheit (that’s 3.33333o recurring in Celsius). If it just has a dial with numbers from 1 to 10, buy a cheap fridge thermometer from a kitchen shop and adjust the dial until the thermometer habitually shows 38o.”