Augustine was born to a Christian mother and a pagan father in A.D. 354 in a town of Tagaste in North Africa. See Augustine in Tagaste in picture above. The main source of our knowledge of his youth and conversions is his spiritual autobiography, Confessions, in which he shows how God lead his early life in spite of his rebellion.
In Carthage Augustine lived disorderly life and took up a concubine, who gave him his only son Adeodatus a year later. Despite of his escapades, Augustine studied rhetoric, and became the most famous speaker in the city (A history of Christian thought by Gonzalez). He studied Cicero's Hortensius to seek the beauty of expression, but found in it a forceful call to search the truth. Augustine acknowledges that in his confession book 3, chapter 4,
In the ordinary course of study, I lighted upon a certain book of Cicero, whose language, though not his heart, almost all admire. This book of his contains an exhortation to philosophy, and is called Hortensius. This book in truth changed my affections, and turned my prayers to Thyself, O Lord, and made me have other hopes and desires. Worthless suddenly became every vain hope to me; and, with an incredible warmth of heart, I yearned for an immortality of wisdom, and began now to arise that I might return to Thee.
This search for truth, however, led Augustine not to Christianity, but to Manichaeism. Augustine was a Manichaean for nine years for three reasons: First, it promised of offering a rational explanation of the universe. Secondly, Manichaeans rejected the Old Testament, as Augustine was never able to accept what he took to be the crassness of Jewish Scriptures. Finally, Augustine had always had difficulties with the problem of how the goodness and love of God could be reconciled with the evil existence of evil. Now this problem seemed to be solved by the asserting that there was not a single eternal pinciple, but two, and that one o these was evil and the other good. However, its weakness was its inability to fulfill the promise of being strictly rational and scientific. Since Augustine became a Manichaean he was skeptical and his teachers were unable to clear the doubts. He was waiting to meet the greatest teacher of Manichaeism, Fautus of Melevis, but the meeting was such a disappointment that Augustine lost his faith in Manichaeism. Augustine decided to go to Rome and then to Milan. It was in Milan that Augustine become Neo-Platonist (Conversion2), and then a Christian (Conversion3).