After using your cast iron skillet, if it does not wipe clean with a paper towel or rinse clean with clear water, just put a handful of kosher salt in the pan and scrub with a damp cloth until all the bits are loosened. This is not seasoning, it's just scrubbing. If you need to reseason the pan rub it well with solid shortening and stick it in a low oven (or a cooling down oven) for a few hours and it should restore the non-stick properties. If you have spots in a pan that always stick when you cook, scrub it out with salt and a wire brush and re-season with crisco.
Before you use your new pan the first time you should wash it with soapy water, rinse well, season and bake it in a low oven. This is the only time you should soap up a cast iron pan. It just gets better the more you use it. I had heard that people who use cast iron pans regularly do not suffer from anemia.