A properly seasoned cast iron pan will have a dark shiny black surface that provides a naturally nonstick surface. The seasoning of a cast iron pan is a polymerized layer of oil that prevents food particles from sticking to the material of the pan. The seasoning is created by coating the surface in a thin layer of oil and then heating it in a hot oven until it dries. Once completed, the seasoning layer cannot be easily removed.
If properly used and maintained a cast iron skillet will last a lifetime. Cooking acidic foods such as tomatoes, will deteriorate the seasoned coating of your pots and pans. You will want to use care in cleaning the cast iron after cooking- don’t soak it in water or the seasoning layer can be destroyed and the pan can rust.
Immediately after every use, I liked to quickly rinse the pan with water and scrub with a brush or coarse sea salt. Most people recommend not using soap in the pan as the emulsification can degrade the seasoning layer.
Reseason your cast iron skillet periodically to restore the non-stick layer of polymerized oils. Rub the skillet with a thin layer of vegetable oil, if you use too much the oil will pool and get sticky. Place the skillet upside down in the oven at 400 degrees for 1 hour.