1- Wash your cast iron cookware by hand. You can use a small amount of soap. If needed, use a pan scraper for stuck on food. For stubborn, stuck-on food, simmer a little water for 3-5 minutes, then use the scraper after the pan has cooled.
2- Dry promptly and thoroughly with a lint-free cloth or paper towel. If you notice a little black residue on your towel, it's just seasoning and is perfectly normal.
3- Rub a very light layer of cooking oil or Seasoning Spray onto the surface of your cookware. Use a paper towel to wipe the surface until no oil residue remains.