My grandmother taught me to use cast iron and it's pretty basic. There used to be a guy called Cast Iron Jack with a fantastic website but I'm not sure he's around anymore, though you'll find his info on other sites, such as
http://www.melindalee.com/resources/reference-center/cast-iron/ and it's right on the money from what I've learned. I do most of my cooking with cast iron and the stuff I use regularly I use corn oil or vegetable oil. The stuff I store or only use occasionally I use mineral oil. A common use for mineral oil is as a laxative so you'll find it on the shelf near that type of stuff. It won't go rancid and comes right off with a bit of hot water before you use it. I have several sizes of dutch ovens and the bigger ones that I only use once or twice a year I wipe down with mineral oil when I store them. Check out the website above and you'll be fine. On whether or not to use food cooked in a pot where the coating had gone rancid, according to the American Camping Association (the organization that certifies resident camps like YMCA, Boy Scout, and Girl Scout camps, at the levels that are involved it'll only impact the flavor. They also recommend mineral oil for storing cast iron.
