I think there's an older thread somewhere around with about ten different recommendations for seasoning.
I've been cooking with cast iron for twenty years, and I confess that I think I have gotten the whole seasoning/cooking/washing thing *right* only within the last three. I tried the bake-to-season method for many years, and cooked with wooden spoons, and tried hard not to destroy the patina of seasoning on the pans with abrasive pads and soap. I had really variable success. It was hard to get crusty stuff off with soft-washing, and the wooden spoons really didn't do a great job of keeping the sediment from burning-on--especially with anything that involved a roux-based sauce. And, of course, all I had to do was deglaze the pan, and it seemed like it would boil-off all the seasoning into the liquid. The next time the pan was used, it would be 'nude'.
The better system now seems to be the Oriental one. 1. To remove any rust, you scrub and wash an old pan as well as possible (wire pads fine), bake at 400 F. until hot, carefully take out hot, put on hob, and then cover the bottom with Kosher salt. After ten minutes, you put a dishcloth in and scrub out remaining rust with the salt. Works well.
2. After rinsing out the pan with hot water and drying, you season by heating it on the hob until very hot. Prepare a 1/4-1/3 cup of oil, and a big bowl of sliced ginger and green onion. You drop the oil into the hot pan and then immediately add the ginger and green onion (which keep the oil from burning and filling your house with smoke). You continue to stir and scrape all of that at very high heat with a steel or cast-iron spoon or spatula (from Oriental food store). Don't be afraid to scratch the iron with the impliment; the whole idea is that the scratches themselves are filled with the carbon over repeated cookings, and the more you scratch it while you cook, the better the seasoning gets. After stir-frying the veggies for ten minutes, dump them, and when the pan is cool enough to handle with a pot holder, put it in the sink with plain hot or warm water. Use something normally abrasive to scrub out any remaining sticking stuff. Oriental shops sell a terrific, cheap scrubber that's like a small broom head made from bundled, split strands of bambo: this works a treat for scrubbing off sticking stuff from a pan surface. Don't use soap.
3. After washing with hot water, you roughly dry out the pan with a bit of paper towel. Then you add a dollop of vegetable oil, and swish it around to coat the inside thinly. Another sheet of towel picks up any excess oil, and then you can leave the pan out or store it away. The oil prevents rust. It also permeates the top layer of the porous, scratched iron.
4. When you cook next, you can quickly rinse and wipe out the inside surface, but really, you probably won't find any oil at all that hasn't been integrated with the pan. I just stick it on the hob, heat, and cook. I use the metal spatuala and spoons--not worrying about scratching (it's good for the pan). When I finish with everything, I scrub with the bamboo brush, rinse, dry, oil-coat, and store. That's it.