Age group(s) for which this technique is helpful:
Preschool and Younger
Elementary School
Middle School
High School & Beyond

Primarily used to improve behavior:
Both At Home and At School

Instructions for using this technique:
The first time a child misbehaves:
Make full eye contact with your child (point your pointer finger in the position as of gestering the number one), and say, "That's one!" If your child repeats the very same behavior, point your index and mid finger in the position as of gestering the number two position, and say, "That's two!" If the child does the very same behavior for the third time, say, "That's three!", then follow through with an appropriate punishment.

Do not allow your child to argue with you while your using this type of method. If the child begins to argue, go on to the next number. Here's an example:
Johnny: "Mommy, I want that candy bar."
Mom: "No, you cannot have that candy bar because it is almost dinner time."
Johnny: "Pleeeeease, pleeeeease, pleeeeease. I have to have that candy bar!"
Mom: "That's one!"
Johnny: "But mom, that's not fair!"
Mom: "That's two!"
Johnny: "Fine! If you won't let me have that candy bar, then I'll sneak it when you're not looking!"
Mom: That's three!"
Punishment, then, follows.

Appropriate Punishments:
Groundings: no bike, no spending the night at their friends house, no internet "play time", etc.
Loss if of priviledges: no TV, video games, phone, or extra curricular activities, etc.
Time-Out: standing in the corner, sitting on a chair, etc.

Other information parents should consider before using this technique:
I learned this technique by watching the 1-2-3 Magic video. My ADD/ADHD support group coordinator suggested this approach. You can find either the book or the video at your local library. If your library doesn't carry them, ask for a request for these items. At the time my two sons were very young. I was very skeptical about something that sounded too easy to do, that is considered extremely effective. Desperate, I decided to try it out. That was over ten years ago, and today I continue to use this technique. In fact, I've passed it down to all the parents, and use the same method for all of my daycare children. This method can be effective with any child ADD/ADHD or not. But, don't forget, the keyword is strict consistency. And, one more thing, NEVER forget to praise your child for his good behavior, not constantly scorn him/her for their bad behavior. Offer rewards and stick to them.