I wasn't aware there was any such rule! Isn't it just a case of being nice, being friendly, being considerate and being polite? If you're all of these, I can't imagine you'll come out with something that would make everyone cringe and upset your date.
Insults are a no-no, but I don't need to tell you this. Oh, and I suppose coming on far too strong is something you might well avoid. Don't let a date feel you take her for granted. She is a person, she matters. Remember that and you're unlikely to say the wrong thing.