“Season” the skillet when you get it. Heat it over high heat until hot and wipe with a thin layer of neutral oil like vegetable or canola, then let cool. Repeat 2-3 times. You can also buy cast iron skillets that come pre-seasoned.
Wash your skillet after every use with hot water and a little soap. Don’t let it stay wet; never let it soak.
Re-season as needed with a single coat of neutral oil over high heat. Let cool. The best way to keep your skillet seasoned is to use it! The more you cook and bake with it, the better the seasoning will be.