In this work, San Eloy offers a number of tips for mediums. Its main objective is to educate practitioners of spiritualism, moralize and reward them through mediumship, that is, the practice of automatic writing through the mediation of spirits. exercise rules, laws for proper application and the most common offenses committed by mediums are explained. Finally, they reproduce -through direct advice or as parable- the best ways to defend against less good causes from the teachings of St. Eloy above all, and Santa Teresa, Jesus or God.