Originally Posted By: DWallach
For brand-new cast-iron cookware that isn't seasoned from the factory, you can brush on a thin layer of bacon grease and put in the oven at nuclear-hot for a few hours.
Don't forget to scrub off the anti-rust coating they put on at the factory, before doing this, or your bacon fat won't do jack.

Take a look here. There's a great post by ThreeGigs part way down the page.