In a cleaning frenzy my roommate scrubbed my cast iron skillet squeaky clean. Though done with the best intentions, I knew the next time I cooked with the skillet would be a disaster. Cast iron skillets can make cooking a dream--non stick, even heating, great heat retension--but only if they are well seasoned. A brand new, unseasoned, or scrubbed cleaned skillet makes everything stick, perhaps burn, and the clean up afterward is a huge pain. But seasoning is very easy and can make a cast iron skillet your favorite pan in the kitchen (it's definitely mine). To season, all you need is a baking sheet, your oven, oil or shortening, and the skillet.
Preheat the oven to 350 degrees. Clean your skillet with hot soapy water and dry it well.
Rub your skillet thoroughly with oil, coating the entire inside service. I have read that flax seed oil works very well, but it can be costly stuff. It's also ideal to use saturated fat when you can, as it protects against rancidity. (palm oil, veg. shortening, bacon fat, lard, etc.)
Place the skillet face down on the baking sheet to catch any oil that might drip out. Put the sheet and skillet in the oven for two hours.
Remove the very hot pan and carefully wipe out any excess oil. There should be find sheen on the surface of the skillet. If not, the skillet needs more seasoning, and you have to repeat this process. 
Simply using it, will keep your skillet seasoned, especially if you have an affinity for bacon. Next time you use and then clean cast your iron, use hot water and a scrubby without any strong grease cutting cleaners. Salt or coarse cornmeal (grits) can be a great abrasive and will absorb some access oil as well.
If your skillet doesn't see much active duty you'll need to season it regularly.
