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:
Read the book, "The Explosive Child", by Ross Greene, PHD. The techniques are his, which he has developed after years of experience with these type of children. I still haven't even finish the book & it's helped already.
Although only in hardback right now, coming in paperback soon, and not cheap, it is WELL worth the money. The book explains everything clearly and logically, if at times a little lengthy.

Other information parents should consider before using this technique:
This technique is something that the WHOLE family incorporates in order for it to work.