The short answer: preheat the empty pan on medium for five to ten minutes, add oil once it is hot, add food once the oil shimmers, and then turn the heat down. That last step is the one nobody mentions and it is the whole difference. Cast iron does not settle at the temperature you set it to: it keeps absorbing heat for as long as it sits on the burner, so a setting that was right at minute five is too high by minute ten. That single property explains almost everything people find confusing about it, including why one manufacturer says food sticks because the pan is too hot while another says maximum heat is what stops food sticking. Both are describing real behaviour at different moments.
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