well before i would just cope with his/her play style......cause they wont listen ..they just want to play their beloved cards that they saw on their ygo shows they watch.
AFterwards i tell how they did.....and they act as if I stole their cards or something. xD or they listen and cooperate.
So I usually teach the kids who listen, tips and strats....but it gets too complicated for them......ive made their decks and maybe play tested once or twice. Now that ive lost some patience and kids are getting dumber and their attention spans shorter im not testing kids anymore. lolz