There are several obstacles that someone who has committed to pray the Rosary will face. Since the Rosary is a long prayer one of the biggest challenges I face is staying focused. If you have read my other posts or if you are just familiar with the prayer, you know that the mental contemplation of the Mysteries is the main focus of the prayer. So getting distracted really detracts from the prayer.
Even if I am only praying 1 chaplet of the Rosary, it still takes about 20 minutes. In that amount of time your mind is bound to wander some. I have found several different things to help me when my mind begins to drift off to the worries of everyday life.
The first is to understand that this is going to happen and be watching for it. If I am not vigilant I can get through a whole decade and realize I have not thought one single time about the Mystery that I should have been contemplating. So before I begin the prayer I make a conscious determination to be watchful of my wandering mind. One tactic that I employ is to try to refocus my mind at the beginning of every Hail Mary.
Another helpful strategy for staying focused is actually a very old one and uses an addition to the "blessed is the fruit of thy womb Jesus" part of the Hail Mary depending on what Mystery you are contemplating. For instance, if you are on the 3rd Joyful Mystery you might add "who took on human flesh" or "who was born in Bethlehem". There is no right or wrong addition, but the addition should remind you of the Mystery.
Another strategy is very similar. Find a phrase or idea from each mystery that strikes you and repeat it and visualize it. For instance if I am contemplating the 1st Luminous Mystery I may repeat and visualize John proclaiming "Behold, the Lamb of GOD who takes away the sin of the world". Sometimes when I am having a very hard time focusing I may rely on this method very heavily.
The very, very best method that I have found to keep my mind from wandering is being familiar with Sacred Scripture. First and foremost, you should be familiar with the specific passages that describe the Mysteries of the Rosary. There are any number of resources to help you find the book, chapter, and verses related to each Mystery. The Scriptural Rosary that can be found at Rosary Army is a good place to start. If you are very familiar with these verses you can call them to mind at the beginning of each Hail Mary.
Although I never make it through an entire chaplet or Rosary without my mind wandering some the tactics above help me to stay as focused as possible and refocus when necessary. The Rosary is a long prayer and my mind will wander to some degree. Still, since the Rosary is a prayer of contemplation I need to fight as hard as I can any distraction so that I might benefit as much as possible from my time contemplating the life of Christ with the Blessed Virgin.