Only say "no" if you mean it. Â - This boils down to the fact that a parent needs to be thoughtful about each and every "no". Â It is amazingly easy to use either "yes" or "no" as a default answer, but default answers lead to situations where you either say "yes" or "no" when the other answer is the more appropriate answer. Â This leads to breaking rule #2...
Never back down from a "no". - Kids learn quickly whether a parent can be whined (or pestered or begged) Â out of a "no" answer. Â So if you say "no", you have to stick to your guns, especially with young children (who tend to test this more). Â
These rules actually help set up and enforce one of an important parent boundaries.  I call it:  "The Mommy said No, Do Not Ask Again  or There Will Be Consequences." boundary. Â
Okay, there is a third rule that applies, but this one applies to every parenting situation - the United Parental Front (or UPF). But that's a different post.