How to avoid distractions during the Rosary

You cannot say your Rosary without having a few involuntary distractions; it is even difficult to say a Hail Mary without your imagination troubling you a little, for it is never still; but you can say it without voluntary distractions, and you must take all sorts of precautions to lessen involuntary distractions and to control your imagination.

To do this:

1) Put yourself in the presence of God and imagine that God and his Blessed Mother are watching you.

2) Imagine that your guardian angel is at your right hand, taking your Hail Marys, if they are well said, and using them like roses to make crowns for Jesus and Mary.

3) Remember that at your left hand is the devil, ready to pounce on every Hail Mary that comes his way and to write it down in his book of death, if they are not said with attention, devotion, and reverence.

4) Do not fail to offer up each decade in honor of one of the mysteries, and try to form a picture in your mind of Jesus and Mary in connection with that mystery.

Source = HERE.