Sent by JackieEditor: Most of the time, a simple rinse under hot water and a scrub with a stiff brush will do the trick. Stuck-on food can be rubbed away with a paste of kosher salt and water.
The two big things to avoid when cleaning cast iron are using soap and letting the pan sit in water. Soap can strip away the seasoning and exposure to water will make the pans rust. This is also why it's good to dry cast-iron as soon as you're done cleaning it.
If your older pan is really gunked up, it might be a good idea to give it a thorough scrubbing and re-season it. Here are step-by-step instructions for both cleaning cast-iron and seasoning it:
Readers, any other tips for cleaning and seasoning cast iron pans?
(Image: Emma Christensen)