She, who has been married to him for 50 years, gets misty-eyed when he brings out a harmonica, long-ago retired, and plays a familiar tune.

He gently teases her about the bargain he got for two dollars - the cost of a marriage license a half century ago.She softly reminds him - "But look at all the upkeep."

She tells a funny story about him and he looks embarrassed, but chuckles. He's pleased by the attention.

They are an adoring couple - an intimate couple - a couple who have spent a lifetime honoring, respecting, and investing in their relationship. The payoff? After 50 years they are still in love.

How do couples preserve their relationship and maintain the conditions most conducive to creating a loving, growing relationship? Here are strategies that can help:

Put the relationship first. C. Edward Crowther, author of "Intimacy: Strategies for Successful Relationships" tells this story about himself and Ingrid, his second wife. Thoughtfully, Ingrid wanted to build a terraced flower garden in their back yard before Edward's 85-year-old mother, who lived in England, visited them for the first time. She wanted to serve his mother breakfast on the patio every morning, giving her a pleasant beginning each day.

Unfortunately, Ingrid ordered the planting soil two weeks too early and did not comprehend how much space was required to store two tons of dirt. When Edward came home late one night he found his car going straight up an enormous mountain of dirt that filled the driveway and blocked the garage door.

Immediately Edward became furious. However, instead of confronting his wife, he took a walk. "The old me would have been very, very cutting of Ingrid, using all my verbal skills to slash and decimate her with sharp words and a biting tone of voice," Edward says. But, as his anger cooled, he found himself thinking these thoughts: "I realized this was the woman with whom I'd be going to bed that night.

"This was the woman with whom, God willing, in the morning I would awaken.

"This was the woman with whom I wanted to share all the joys and sadnesses of life - and this would be going on for as long as we both were alive.

"Was I going to risk injuring my relationship with Ingrid over a pile of dirt?"

The answer was no. Edward headed for home armed with a fresh and very personal understanding of commitment and worked out the problem amicably. He put the relationship - and his wife - first in face of a major difficulty.

Become good friends. Most couples who have successful marriages report they are first of all friends. Friends listen and share secrets. They work and play and hang out together. And they laugh a lot.

An Arabian proverb captures the essence of such friendship: "A friend is one to whom one may pour out all the contents of one's heart - shaft and grain together - knowing that the gentlest of hands will take and sift it or keep what is worth keeping and with a breath of kindness blow the rest away."

Acknowledge your spouse's strengths. "In every marriage over two weeks old, there are grounds for divorce," says one author. "The trick is to find grounds for staying together."

Never mind that your husband doesn't know a car muffler from a carburetor or that he becomes unglued if he has to play plumber. He's a hard worker and he's good to the children.

Never mind that your wife sometimes doesn't balance the checkbook and "overspends" once in a while. She's a warm, nurturing mother and she makes terrific meals.

The point is: love your spouse for what he or she is, not for what you think that person ought to be.

Opt for an imperfect marriage. Couples are often misled to believe there are "perfect marriages."

There's no such thing, says Linda Wolfe, the author of an article called "Imperfect Marriages." There are only imperfect marriages and bad marriages.

And what is an imperfect marriage? "It's a relationship in which the pleasures vastly outweigh the pains. An imperfect marriage may contain deprivations, even anger, but both partners feel content and remain genuinely interested in one another's well being - at least most of the time. Unlike a bad marriage, the imperfect kind is well worth hanging onto."

How can you tell the difference? In a bad marriage, spouses inflict serious emotional injuries, making each other feel worthless, helpless, crippled. In an imperfect marriage, the hurts exchanged are what might be called psychic scratches.

Opt, then, for "one of of those wonderful, deliciously inspired imperfect marriages," Wolfe says, "because, you see, there are no others."

Note: This article is a tribute to the author's parents, featured in the introduction, who taught her most of what she knows about love.