I think they should discuss the areas within marriage that will call for decision making before marriage, such as finances, children, discipline, relative importance of work, possessions, home, faith life etc. They don’t necessarily have to agree on details but they should both be operating from the same underlying assumptions and beliefs. For instance, if one considers life is an adventure, and would like to live and work on various parts of the world, and the other refuses to even consider moving away from their family, their is a problem. If one considers saving for retirement and education a major need, and the other thinks money is to spend, there is a problem. If one feels God should be the center of the marriage, and the other feels any religion is okay as long as it only interferes with life on Sunday (and then only before noon), there is a problem.