Voltaire's approach to education and child rearing was a consequence of a wider philosophical system, which in many ways opposed traditional modes of thought and habits common in the France of his period. In a sense, his theories were as much negative suggestions about how one should not raise a child as positive suggestions about how one should do so.
The first strong negative belief we find in Voltaire was his opposition to all forms of superstition and priestcraft. He objected strongly to the Jesuit education he himself had received, and generally of the predominant practice in France that placed education mainly in the hands of Roman Catholic monastic orders. He advocated a secular form of education.
Next, although he was opposed to Jesuit education, he was equally opposed to the system of Rousseau, doubting the inherent goodness of the untutored child and favoring critical thinking over Romantic intuition.
Next, after the Lisbon earthquake, Voltaire turned against the optimism of philosophers such as Gottfried Wilhelm von Leibniz, arguing in Candide that such points of view ill-prepared young men for the real world.
For positive precepts, Voltaire would want young people educated in the sciences and critical thinking, taught to analyze the world rather than to accept the word of authorities.