1. Place your rusty skillet in the sink and sprinkle a couple tablespoons of salt into it.
2. Take your chunk of potato and start scrubbing. The moisture from the potato will be enough to help the salt dig in to the rust.
3. The salt will get dirty very quickly. You may choose to rinse out the pan to survey your progress. If there is still rust, add more salt and repeat Step 2.
Complete instructions here: http://bit.ly/HLHZuL