Cast iron is not difficult; it is just badly explained. The whole job is getting a
very thin layer of oil hot enough to change chemically, and then repeating that until the
surface is glassy.
The method
Wash the pan warm and dry it completely on a burner — water is the enemy, and a
pan that looks dry is usually not. Put half a teaspoon of a neutral high-smoke-point oil in
and rub it over every surface, including the handle and the underside. Then, and this is
the part everyone skips, wipe it back off as if you made a mistake. What is left is the
right amount.
Put it upside down in a 450°F oven for an hour and let it cool in the oven. Repeat
three or four times if the pan is new to you.
What ruins it
Too much oil, which pools and cures sticky rather than hard. Soaking it. Putting it away
damp. Acidic sauces simmered for an hour in a pan whose seasoning is still young.
What does not ruin it
Soap. A little dish soap on a well-seasoned pan is fine and has been fine for years.
Metal utensils are also fine — polymerised oil is tougher than people think.