First of all, your kid needs to be old enough to understand what is happening and what you are saying, because secondly, you are going to have to tell them, "Kid, this behavior isn't ok and until you can act nicely I am not going to pay any attention to you." Now to be fair to them, you need to tell them exactly what kind of behavior or magic word or what it will take for you to pay attention and what kind of behavior is NOT ok. Don't leave them to guess, tell them! Thirdly, you got to pull out the stops and put on your best Hollywood persona and act it up. Finally to make this a successful art, sometimes you just got to give in. Being a hardnose may not work in all situations, so keep a short list of when you might let that behavior slip by unignored in favor of thwarting off something worse, like a huge temper tantrum because your child is really hungry or tired and is trying to tell you they love you. :) Let me give you an example.
My youngest son
That morning sure enough, Isaac woke up in the same manner in which he went to sleep. Gibber gabbering and putting on his best "I'm a wittle baby" look. So the first time he baby-talked, I told him "You are a big boy and when you talk like that I don't know what you are saying. I need you to talk like a big boy so that I can understand you." Of course, he didn't care what I had just said, because it didn't concern him...yet. But the first time he said something like a baby I kept right on with what I was doing. Of course he got louder and louder in his babytalk voice and almost got hopping mad. It was then that I looked up slightly, using my best acting ability, as though he had just whispered something at me instead of yelling and told him "I'm sorry, hon, I didn't hear what you said. What was that again?"
The look of surprise on his face was so funny that I had to look back down. He had been on the point of losing it, but when I pretended like I just didn't hear him he paused a little and looked, well upset but confused. But true to his own goal and devotion to becoming the baby again, after all, he now had my attention again, he repeated his question again in that same whiny baby voice.
Well, I wanted to scream-I wanted to run away-I felt failure creeping up on me, but...my response to him was a very cool and calm "what?" instead. Without skipping a beat, he responded in the same voice and I responded with my very best attempt at pretending that I genuinely couldn't hear him: "What?" We had a brief tennis match right there and then. He lobbed his baby talk at me and I responded with my best doe-eyed confusion. With each "what?" I responded with I felt my blood pressure rise just a little and I wondered what was giving him such strength. After all, I had a goal, I had a plan and I was in control...barely. How did he manage to test my resolution so thoroughly. I knew it would be a fight, but I was close to breaking a sweat!
Finally, after seemingly repeating himself endlessly in that same baby voice-my son-who has the conviction of one twice his age and had already seen what power that baby-talking had over me the night before-seemed to swagger a little. His adorable little eyes were now showing signs of strain. He was was going to lose it soon and I was going to lose my opportunity to show him how this thing worked. So now I sucked it in and keeping my cool, (I think the veins in my temples were bulging slightly) I told him, "Isaac, I don't know what you are saying, can you use your big boy voice please?" It worked!!! Hallelujah! I could have sung at the top of my lungs. In his regular voice, now just a little deeper, he spoke to me! It was a breakthrough that would carry me through the next couple weeks of the battle.
This breakthrough didn't cure the baby-talking completely right then and there, but it did work and it gave me the resolution to ignore the baby-talking strategically and the hope that I wouldn't be living with a baby-talking teenager in ten years. Which was awesome too. We had many repeats of our stand-off that first morning that I ignored him. There were also many times where I lost and chose not to ignore his baby-talking on something important or non-negotiable-which turned out to be pretty much anything relating to hunger and food or the toilet. I enlisted the help of my husband and my sister too. Having someone in the trenches helps because you can always tag-team. We all became pretty good actors if I must say so myself.
So in short, ignoring your kid can be an art if you set the rules on what will be productive and then stick with it. I suggest getting back-up because kids are smart and they know how to push our buttons. Good luck!
Now for your kids who like to play on the computer, check out these games for kids a the Big Fish Game website.
Other Resources I recommend: