Normally a domestic freezer is best set to −18 °C (0 °F) or colder, as that's what the expiration dates for many food items are based on. It's also a requirement for freezers in restaurants, supermarkets & other places that sell food (at least here in Europe) to maintain a temperature of at most -18 °C. A general purpose domestic fridge should be at around 1-4 °C (so, just above the freezing point, and below 5 °C).