no soap, and avoid acidic foods
I've recently been making a lot of sugo all'amatriciana in my cast iron, which involves deglazing the pan with a bit of red wine vinegar before stirring in tomato paste and simmering down - I've not seen any ill effect on the seasoning of my pans at all. Maybe when working on seasoning a pan it's not advisable, otherwise I can't see any reason not to cook acidic foods when you've got a well seasoned pan