Some say avoid using soap to clean your cast iron skillet, I think it's fine to use it as long as you maintain the skillet afterwards. Clean the skillet using a sponge, hot water and a little bit of soap. Once clean, dry the skillet completely and place it on medium high heat. Pour about 1 tablespoon oil into the skillet and immediately rub it all over the the pan using a paper towel. Turn the heat off and let the skillet cool completely before putting it away.