The Most Effective Form of Prayer

The most efficacious prayer of the Church is the holy sacrifice of the Mass, because it is a sacramental re-presentation of Christ’s own sacrifice on Calvary to the Father. As for the forms of prayer you named, the Liturgy of the Hours is not a personal prayer devotion but a part in the Church’s own daily prayer to God.

As for strictly personal devotions, such as the rosary, litanies, chaplets, novenas, etc., their efficacy depends on God’s love for us and on the virtue of the petitioner. Although God listens to all prayers because he loves us, the prayers of a virtuous person are more efficacious than those of an obdurate sinner—cf. James 5:16.

Generally speaking, though, we should not focus on which prayers we think will “work” but on opening our hearts and lifting up our minds to God.