I would answer that I think it is different for boys and girls. That girls have definite ideas and are far more opinionated about what they want to wear younger. I know for many parents this begins as early as 3 or 4 years old although as I only have a boy I haven't experienced it myself. My boy was very easy about clothes and only began to have a strong idea and preferences at around 12 years old. I think the key with the younger girls is to let them have some leeway with choices but to give them the variants so its not complete anarchy. You know, would you like the pink top or the red. That kind of thing, then there is some autonomy for them but you retain control of it too. By 8-10 years old however they will want to be shopping with you and will have very clear ideas in mind. Then its a case of trying to steer them to the more age appropriate styles and by then peer pressure will come into play as well.