The best marriages are made by people who begin their relationship as friends and use friendship as their marriage model.
Do you know how to make and keep a friendship? Listen and talk, share work and pleasure, respond to a friend's bids for attention, and get some attention back? Laugh and enjoy each other, be flexible when things don't work out, fix your disagreements, stay loyal but open to other people in your friend's life? If you do, and can keep these skills going with people your own age, you already know how to sustain a marriage.
The dramatic stuff of romantic attachment, the wash of sexual attraction, the focused desire for only that one partner: that biological experience, which is the core of nearly every popular song or relationship movie made in the last 50 years, is a piece of human experience, too. But it is crushingly brief. Most of us will only sustain that brain and body phase for 12-18 months. After that, we begin to readjust to a steady attachment that looks and behaves more like a close friendship than any other relationship we have. Friend with benefits? That's what a solid, happy, sustainable marriage is.
The best preparation for a happy marriage is not a long dating history, a series of broken engagements, or even one marriage after the other. The best marriages are made by those who have learned how to make and keep friendship relationships. Who'll will stand by you in difficult times, visit you when you're sick, and share their ice cream? That's who you want at your side when the real rubber meets the road: a dear friend. Your spouse.