What to read in preparation? (1) Calvin’s Institutes, (2) Reformed Confessions, (3) any of the books written by professors of the seminary you want to go to, (4) Van Til, Christian Apologetics, (5) Machen, Christianity and Liberalism, (6) Kuyper, Lectures on Calvinism. Hope that’s of some help. May the Lord guide you in these important and difficult decisions.