An excerpt from a letter written by Saint Pio of Pietrelcina (Padre Pio), 1915

In order to avoid irreverence and imperfections in the house of God, in church, which the Divine Master calls the house of prayer, I exhort you in the Lord to practice the following:

Enter the church in silence and with great respect.

Among other pious considerations, remember that our soul is the temple of God and, as such, we must keep it pure and spotless before God and His angels.

Then take holy water and make the sign of the cross carefully and slowly.

As soon as you are before God in the Blessed Sacrament, devoutly genuflect.

Once you have found your place, kneel down and render the tribute of your devotion to Jesus in the Blessed Sacrament. Confide all your needs to Him along with those of others.

Speak to Him with filial abandonment, give free rein to your heart and give Him complete freedom to work in you as He thinks best.

When assisting at Holy Mass be very composed when standing up, kneeling down and sitting, and carry out every religious act with the greatest devotion.  

Be modest in your glances; don’t turn your head here and there to see who enters and leaves.

Don’t laugh, out of reverence for this holy place and also out of respect for those who are near you.

Try not to speak to anybody, except when charity or strict necessity requires this.

If you pray with others, say the words of the prayer distinctly, observe the pauses well and never hurry.

In short, behave in such a way that all present are edified by it and, through you, are urged to glorify and love the heavenly Father.

On leaving the church, you should be recollected and calm. First, take your leave of Jesus in the Blessed Sacrament. Do not leave Him without asking for and having received His paternal blessing.