This book was written specially for young Catholics, but would probably be of interest to other Christians as well. It's quite vintage (I think 1930s-40s, judging by the fact that movie theaters and driving around for fun are mentioned, but TV is not) but I heard it's still recommended in more trad Catholic circles even though some parts of it could possibly offend modern sensibilities.
It goes into great detail about dangers of s*xual sin, while the last chapter is all about choosing a mate. I guess the idea of never marrying outside the Catholic faith could be offensive to some, but if you extrapolate it to never marrying unbelievers, you'll realise that the author isn't really that far from the truth.
This is an interesting piece of advice:
Refrain from beginning to keep regular company too soon. If you begin to do so at sixteen or seventeen years, you expose yourself either to the danger of a premature marriage with its frequent mistake of poor choice or you court the hardly lesser evil of an immoderately long courtship with the attendant disadvantages. You tie yourself down to one person and thus lose the social advantages and contacts that will have a great influence upon your later life. You expose yourself in a special way to temptations against chastity, because this love affair may be a very prolonged one, and the danger of violating chastity increases as the affection is prolonged.
If you begin “to go steady” while you are a student, you will find it almost impossible to do justice to your studies. Since courtship limits your interest to a single person, it should not be undertaken until you are in a position seriously to consider marriage in the not too distant future. This presupposes that you have attained the age to understand the great responsibilities of marriage and that you have enough financial resources to establish and maintain a home.
It goes contrary to what some Christians online teach about every young girl needing to marry at 18, doesn't it?
Marrying in haste nearly always means repenting bitterly at leisure. Do not prefer to be sorry to being certain.