The best way for the faithful to assist at the sacrifice of the Mass is to offer to God, with the priest, the divine Victim, to remember the sacrifice of the Cross, and to unite with Jesus Christ through sacramental communion, or at least through spiritual communion.
No other worship practice of the Catholic religion is more holy, no other procures a greater glory to God, no other is more useful for the salvation of souls than the holy sacrifice of the Mass, in which may be found so perfectly all the fruits of the Redemption that Christ accomplished through His Passion and His death on the Cross.
So Catholics frequently assist in this august and divine sacrifice, that your soul, on hearing it, may have the same sentiments of ardent piety as it would have had on Calvary in the presence of the dying Christ.
Concretely, hearing the Mass with devotion means:
—To unite, from the beginning, your intention to that of the priest who offers to God the holy sacrifice for the end for which it has been instituted;
—To follow the priest in each of the prayers and the actions of sacrifice;
—To meditate on the passion and death of Jesus Christ, and to detest with all your heart the sins which have caused it;
—To make a sacramental communion, or at least a spiritual communion while the priest communes.
The recitation of the Rosary, or other prayers during the holy Mass do not impede fruitful hearing of it; provided that one tries as much as possible to follow the ceremonies of the holy sacrifice. It is very laudable to pray for others while assisting at the holy Mass, especially to pray for the intentions of the living and the dead.