Here's a pretty well known link to seasoning cast iron.
http://sherylcanter.com/wordpress/2010/01/a-science-based-technique-for-seasoning-cast-iron/
That article generated quite a bit of debate over the oil used when it was first published. I would caution anyone following her advice to know exactly what type of oil you are using. Also to be noted regarding the title is that nothing in her bio reflects a background in chemistry.