Best way to clean Cast Iron pans

I read this in Who Knew? and was happy to find a way to keep me from throwing out my tarnished cast iron pans.
Cover the stain with a paste of cream of tartar and white vinegar.
Apply liberally, let sit, then scrub with a damp soft cloth.

I also read that rubbing them down with a little vegetable oil now and then helps extends its life

*now if only I could find out what to do for that dying basil plant