Cast iron pans must be seasoned. Most pans today come pre-treated, but do it again. Wash the pan with a little water and dry well. Soak a paper towel with vegetable oil and rub all over the pan. Keep swabbing until the pan has a sheen. Heat the oven to 350°F (180°C). Place the pan upside down on the middle oven rack (put some foil on the rack below to catch any drips) and bake for 1 hour. Turn off the heat and let the pan cool down inside the oven. It is now ready for cooking.
If you buy only one pan then buy a 10-inch (25-cm) pan—a 12-inch (30-cm) pan is a good size for big steaks and vegetables.
Remember to cover the handle when you take it out of the oven to avoid burning your hand.
Wash with warm soapy water and dry immediately. Coat with a little oil the first few times you use it.