I think there is one thing that all 3 year olds have in common, and that is the desire to push their boundaries and limits. Parenting books (yes, I read them!)...Supernanny (I wish she would come to my house!)...you name it they all tell you to be firm, otherwise your child will quickly learn what is, or is not, ok.
With Ava recently, this struggle has been at bedtime. Here's the problem/opportunity/challenge (insert your favorite word here), when she comes out of her room again and again, it's not for more water, it's not to go potty, it's to give Mommy or Daddy one more hug and kiss.