"Daddy date night" to model the standard for your daughter; anyone treats her less than that have nothing to do with him.
Everyone is someone’s future spouse (or at least espoused to Christ). Don’t do anything with them you wouldn’t do with someone else’s spouse.
Do not pray together. Too intimate.
Have checklist, e.g., must be(come) Lutheran. Every date a potential spouse.
End it by third date if not heading toward marriage; beyond that you can't think clearly, only emotionally.