With DS I'll give him my "look" or say "Excuse me?" and most of the time, he'll apologize and/or rephrase.
I've only been in SD's life for about 2 years, so she's not quite used to my parenting style. SD will use baby talk from time to time. It drives me nuts! The 1st time, I remind her that she's 9 and a big girl and tell her that I would like her to talk like it. The 2nd time, I'll prompt her with a, "How are you supposed to ask?" After that I'll just stare at her (not answering) until about the 3rd time she repeats herself, when she clues in. When she's being disrespectful, I do sort of the same thing. I'll clue her in on the behavior, then give her a warning, and then I'll ignore it. She's the type who will repeat the same thing over and over until she gets a response. She's picking up on my "look" however!