It is very important that your child not know your ulterior motive when you purchase the Xbox 360 for them.  They should believe that you are only interested in their enjoyment and pleasure.  If they suspect that you are going to use the machine for your own benefit they might not allow themselves to become hooked on the system.  The gaming addiction is your best friend and you will need them to become thoroughly enraptured by their gaming world.

When the game system is in the home, you will have to supply a large selection of fun and entertaining games for your children so that they become completely addicted.  This will not be the most difficult part of your task.  You should take them to the store with you so that they can help select the games that will be their undoing.

For a couple of weeks let the enjoyment of the Xbox 360 wash over your children.  They should be given as much freedom with the machine as possible so that they are completely immersed in play.  When you are sure that they are fully hooked on the game, it can be used to your advantage.  It will become the perfect privilege for you to take away when your child is not behaving appropriately.

All kidding aside, if you find that your children are attached to the free Xbox 360, you can use it to help you with your parenting.  A punishment is only effective if it means something to the child.  When the child misses playing their game it will force them to find ways to avoid losing it again.  This should help you with most child behavior problems.  However, there are some cases where it will not work.  These children quickly move on to other activities to occupy them when they are no longer able to play with their game console.

Taking away the Xbox 360 should work for most children.  For those that do not respond to this type of behavior modification you will most likely find that it does not matter what you take away, a different type of method will be needed.