You should be Catholic, unmarried, free of family obligations etc.
You should be in good physical and mental health. The monastery must be assured that you can respond to the demands of close community living and contribute toward its need to earn its daily bread.
Since monks take a vow of obedience, you must be able to live with good will toward authority.
The monk is vowed to a celibate life, and his need for love and friendship must be found within the monastic life.
One of the monk's most challenging ascetical practices is to learn to accept his brothers as they are and be open to their criticism of his own faults. For this reason, the person who aspires to live monastic life must be able to let go of his own ideas and preferences when the majority of his brothers want to move in a different direction.