Caring for your cast iron cookware
Seasoning your pan is, of course, paramount. But even so, the iron is still very prone to rust. Therefore, the first rule of cast iron cookware is to never let it soak in water. Obviously this becomes impossible once something dries on, so make sure to always clean it shortly after use.
The slightly lesser known, but equally important tip is to avoid soap when cleaning. The surface of the pan is very porous (which is why it needs seasoning to begin with), so when you apply soap it breaks up the grease and gets in the little cracks and stays there forever. Not the end of the world, but something most would probably rather avoid. A common technique for cleaning is to wipe out the grease with a paper towel, then wash with a clean sponge and dry immediately. Do this every time and your cast iron skillet will be better than mom's!
Roninspoon adds: Many people, myself included, scrub their iron cookware with water and salt. Not only is the salt gritty enough to act as a cleansing scrubber, but the salt has the added benefit of preventing any cooked on grease from going rancid