How to take care of cast iron pans and create a great patina for cooking:

• Scrub the pan with a stiff plastic brush in soapy dish water.  Use steel wool if you need to remove rust.
• Dry with a cloth, and then dry more thoroughly by putting on the stove over medium-low heat for a couple of minutes.  
• Turn off pan and add a blob of shortening.  The residual heat from drying the pan will probably melt the shortening.  If not, turn the pan back on for a few moments just to melt it.
• Spread the melted shortening around the inside of the pan making sure to get it all the way up the sides. 
• Remove all the excess shortening with a piece of paper towel.  You just want a light, even coating.
• Place upside down in a 325 degree oven with a cookie sheet or something on the rack below to catch any drips.  
• Bake for 1 hour.  Turn the off oven and leave pan in oven until cool.

Voilà!  A reconditioned cast iron pan!