Many men date a women based off her personality and looks.
However, the women they marry probably won't be as attractive as his other girlfriends, and there are popular theories for this.
After dating a lot, guys tend to know who they can and cannot get along with. Marriage is forever (supposed to be), so it's important to marry someone that is willing to help them, support them, and be a friend.
The main thing girls need to work on the most when it comes to marriage qualities is their temper. I know it's a stereotype, but many women have short fuses. If a woman is constantly complaining, she may disqualify herself in the minds of many men for marriage.