Make time to connect lovingly with your spouse every day
A couple can significantly improve their chances of marital success by devoting as little as 15 minutes a day exclusively to each other. For instance, choose to go to bed a little earlier and wake up a little earlier, and spend the extra time in bed cuddling, making love, and reaffirming your love for each other. Take time every day to have meaningful conversations with each other; to listen with the same intensity as when you were dating; to touch, hug, and show affection; to tell each other how you feel about your marriage; and to talk about your goals for the marriage and your lives.
Compliment your spouse regularly -- both in private and in front of others
Even if your partner seems embarrassed or shrugs it off at first, the glow from sincere praise lasts a long time.
Love your spouse in the way he/she wants to be loved
We often make the mistake of assuming that the things that touch our hearts the most deeply will affect our partner in the same way. For instance, you may think red roses are the perfect Valentine's Day gift, but to your spouse, they represent a waste of money and an allergy attack. If you don't already know, find out what your spouse yearns for, and then deliver it with love -- and no comments about how "stupid" it is to want a cordless drill/a picnic on the living room floor/a tuna casserole, etc. Remember: the best gift is something your spouse wants -- not merely something you want him/her to have.
Take care of your appearance
Look your best for your spouse: he/she deserves it. Lose the ratty sweat pants or frayed sweater he/she hates so much; you can find other comfortable clothing that aren't a complete turn-off for your partner. This also means taking care of your health.
Dr. Finnegan Alford-Cooper studied 576 couples who had been married for 50 years or more; she released her findings in a book entitled For Keeps: Marriages that Last a Lifetime. In her study, she found that 95% of the spouses agreed that fidelity was essential to a successful marriage, and 94% agreed or strongly agreed that marriage is a long-term commitment to one person. And these "lifers" weren't making the best of a bad lot: a whopping 90% of the couples she surveyed said that they were happily married after 50+ years.
Do things together
Another common factor of long-term happy marriages is that the spouses regularly do things together that they find fun and exciting. Whether that's ballroom dancing, bowling, playing cards, SCUBA diving, or skiing, participate in at least one activity that you both enjoy every week. If you have kids, make sure at least half of these activities are for you and your spouse only.
Spend time apart
You take a pottery course while your spouse plays hockey; you play bridge and your partner collects stamps. You don't have to love everything your partner loves, but you do have to allow him/her the freedom to pursue cherished hobbies. An added bonus is that separate interests can generate interest between you.
Be friends with your partner
According to John Gottman -- a psychology professor who claims his research will predict with 91% accuracy whether a couple will stay together -- the key to marital happiness and success is friendship. Some of the most important aspects of this type of friendship are knowing each other intimately, demonstrating affection and respect for each other on a daily basis, and genuinely enjoying each other's company. Gottman based his findings on 25 years of marital research, which he presented in his book The Seven Principles for Making Marriage Work.
The Terms of Endearment
Flowers, candy, cards, and gifts are all wonderful tokens of love on Valentine's Day, but if you really want your romance to last, you must practice some marriage-saving steps. Most disputes that break up marriages are over sex and money. Don't let surprises lead to trouble. Valentine's Day reminds you to be flexible and that you have to give to receive.
Say "I love you" every day
This is especially important when you're not feeling the sensation of love; at these times, you have to actively generate it. Saying those three little words, and performing loving gestures, will warm both your and your spouse's hearts.