Never store food in cast iron.

Never wash cast iron in a dishwasher.

Never store cast iron utensils wet. 

Never go from very hot to very cold, and vice versa; cracking may occur.

Never store with excess grease in pan, it will turn rancid.

Never store with lids on, cushion lid with paper towel to allow air flow.

Never boil water in your cast iron cookware - it will 'wash' off your seasoning, and it will require a re-seasoning.

If you find food sticking to your pan, it is a simple matter to clean the pan well, and set it up for a re-seasoning, just follow the same steps. Don't forget that dutch ovens and griddles need the same attention as a cast iron skillet.