Normally, one would need a man and a woman who are both free to marry, not already married, or committed by vow to not marry; having full consent of the will. They should both be Catholic, and as it is a sacrament, they should have both made a good confession. It must be before a priest of the Church with witnesses. The consent must be an act of the will of each of the contracting parties, free of coercion or grave external fear. It must be open to children. It is a complete unity and fidelity, and indissoluble, both parties must understand this and consent to it. It is a sacrament that mirrors the love that Christ has for His Church, and is an image of that relationship.