I heard someone speak about cast iron cookware at the Weston A. Price Foundation's 2010 conference. I had already been using it for several years and was well aware of the dangers of non-stick coatings, but he gave me another reason to love it:
It's a very important decision when shopping for cast iron because it will last so long. I chose pans with lids. That's probably the most important consideration. I use the lids almost as often as I use the pans.
Another consideration is the manufacturer. Newer cookware made from reclaimed metal may contain some heavy metal toxins, especially if it was manufactured in a foreign country with less stringent regulations than the United States.
Lodge is a good company. Unfortunately all of their cast iron cookware now comes preseasoned with bad oils, but this can be burned off and reseasoned with the proper coating.
The age of the piece is not important. You can fix up old cast iron by burning it or power sanding it to remove the rust and then reseasoning it. It should be reseasoned immediately.
For the initial seasoning, the pans need to be coated all over (including the outside) in a saturated fat. You can use tallow, lard, or coconut oil. Place them upside down in a 450°F oven for 30 minutes with a tray underneath to catch any drips. Allow them to cool in the oven for 2 hours.
Each time you use the pan, liberally coat the cooking area with fat or oil. Cooking some bacon occasionally helps, too. A natural non-stick coating will build up over time. If you notice any rust spots starting to form, rub a little saturated fat on them until they disappear.
It should never be submerged in a tub of hot water nor touched by soap. I rinse out the bottom with hot water, scrubbing with a soft rubber brush, and hand dry it immediately.
That speaker I heard said that his family does not clean it until they are ready to use it again. They clean the pans by rubbing them with olive oil and salt. I would be curious to see what the pans look like with this constant treatment, but I'll stick to my own method for now.