The three specific requirements of Conjugal Love.

Here is what Pope Emeritus Benedict XVI said on the subject:

Dear friends,
Every human love is a sign of the eternal Love that created us, and whose grace sanctifies the choice of a man and a woman to entrust their life to each other in marriage. Live this time of engagement in the confident expectation of this gift, to be welcomed through a path of knowledge, respect, and attention that you should never lose: it is also the condition for the language of love to take its full significance over the years. Educate yourself from now on to the freedom of fidelity, which leads to taking care of each other, to live for each other. Get ready to choose with conviction the "forever" that characterizes love: indissolubility, more than a condition, it is a gift to be desired, sought and lived beyond the uncertainty of any human situation. And do not think, along with a widespread mentality, that cohabitation is a guarantee for the future. Leapfrogging eventually "burns" love that instead needs to respect the times and the different stages of its expressions; it needs to leave space to Christ, who is able to make human love faithful, happy and indissoluble. 
The faithfulness and continuity of your love will enable you to also be open to life, to be parents: the stability of your union in the sacrament of matrimony will allow the children God entrusted to you, to grow up with confidence in the goodness of life. 
Fidelity, indissolubility and openness to life are the pillars of any family, the true common good, a precious heritage for all of society. From now on, establish on them your path towards marriage and witness it also to your peers: it is a valuable service! Be grateful to those who, with commitment, competence and availability, help you in your formation: these are signs of the attention and care that the Christian community offers you. You are not alone: ​​before anything else, look for and welcome the proximity of the Church. 
PASTORAL VISIT TO ANCONE, Excerpt from Meet the Young Lover, ADDRESS OF HIS HOLINESS BENEDICT XVI, Plebiscito Square, Ancona, Sunday, September 11, 2011.
http://www.vatican.va/holy_father/benedict_xvi/travels/2011/index_ancona_en.htm