Christian meditation (thinking deeply on Scripture) is "the missing link between Bible intake and prayer." If there was a "secret" to George Müller's prayer life, it was his discovery of the connection between meditation and prayer. Müller's discovery was that after meditating on Scripture he was more able to experience a meaningful prayertime.
-Donald S. Whitney, "Spiritual Disciplines for the Christian Life" (partial quote and partial paraphrase).