There are many answers to our question. Some would say marry someone who shares common interests and goals, someone with the same educational background, same religion, etc.
The fact is:

Recognize God’s authority. When two people contemplate marriage, they must recognize some source of authority, whether it is a human philosophy or God Himself. Beloved, God is the author of marriage (Gen. 1, 2).

It was God who said, ” it is not good that man should be alone; I will make him an help meet for him” (Gen. 2: 18). God then instituted marriage (vss. 23-25). God, consequently, is qualified above all to tell man how to have a good marriage.

We can enjoy a good marriage by observing God’s order and
teaching. The husband/wife relationship has precedence over all earthly
relationships (Gen. 2: 24). Their union is indissoluble, except for death and
adultery (Matt. 19: 4-9). God’s order is: the husband is the head of the wife,
the wife is to be subject to her own husband, and the children are to obey
their parents (Eph. 5: 22-6: 1). Parents, especially fathers, have the awesome
responsibility of rearing their children “in the nurture and admonition of
the Lord” (Eph. 6:4).

Husbands are to love their wives and wives are to reverence their husbands. Paul wrote,
“Husbands, love your wives…” (Eph. 5: 25). Beloved, a point of great importance is “love” is from the Greek agape. Most men do not need urging to physically love their wives, but what is being taught is a love, which is much deeper. Agape love is unselfish and seeks the best for the one so loved (Eph. 5: 25-29). Wives must respect their husbands (Eph. 5: 33). In such a marriage there is trust and unison of effort and direction.