In most cases of nagging, it is very difficult to deal calmly with a child that is wearing you down. One way I have found to get the nagging to stop (aside from giving in) is to raise my voice, get angry and make my kids sorry they asked for the eleventh time. But ah-ha! I have found another rhetorical option. In this approach, you calmly give them a point of obedience, and if they disobey you, you can enforce it as you would enforce any other obedience issue.
Kids, at 9:30AM: "Can we have a treat?"
Mom: "Yes, you may. AFTER lunch."
(two minutes later...)
"Mommmmeeeee, can we have a treeeeeeeet?"
"I already answered that question. Do you remember what the answer was?"
- If they don't, then repeat the answer and then ask them to tell you what you just said (having them repeat the answer will cement it in their brain and give you the assurance that they have heard and will likely remember the answer next time they ask).
- If they do remember, have them tell you what the answer was and then praise them for remembering.
Using these words takes a behavior that is otherwise just annoying and tiresome and difficult to discipline for and turns it around into a very simple obedience issue. Sneaky, huh?