In addition, a lot of enamel will just stain after some time, which is normal; This is why some of the vendors are just going with black enamel these days, instead of the long-used white. I haven't tried baking soda to clear up the stains on mine, I'll have to give it a shot.

Also, if the enamel cracks inside the cooking area of the pan, you may want to throw out the pan; it may expose your food to contact with toxins used in adhering the enamel.