I came across this list in Daniel Akin’s book God on Sex: The Creator’s Ideas about Love, Intimacy, and Marriage and thought it was really helpful:

1. Work at it. A lifetime of love and romance takes effort. Few things in life are as complicated as building and maintaining an intimate, passionate relationship. You need to work on it constantly to get through those trying periods that require extra work.
2. Think team. When making important decisions, such as whether to work overtime or accept a transfer or promotion, ask yourself this question: What will the choice I am making do to the people I love? Talk with your mate and family. Make “we” decisions that will have the most positive impact on your marriage and your family.
3. Be protective. Guard and separate your marriage and your family from the rest of the world. This might mean refusing to work on certain days or nights. You might turn down relatives and friends who want more of you than you have the time, energy, or wisdom to give. You might even have to say no to your children to protect time with your spouse. The kids won’t suffer if this is done occasionally and not constantly. It will actually be beneficial for everyone!
4. Accept that good and not perfect is okay when it comes to your mate. No one is perfect other than Jesus! You married a real person who will make real mistakes. However, never be content with bad. Always aim for great, but settle for good!
5. Share your thoughts and feelings. We have seen this one over and over. Unless you consistently communicate, signaling to your spouse where you are and getting a recognizable message in return, you will lose each other along the way. Create or protect communication-generating rituals. No matter how busy you may be, make time for each other. For example, take a night off each week, go for a walk together on a regular basis, go out to breakfast if you can’t have dinner alone, or just sit together for 30 minutes each evening simply talking, without any other distractions.
6. Manage anger and especially contempt better. Try to break the cycle in which hostile, cynical, contemptuous attitudes fuel unpleasant emotions, leading to negative behaviors that stress each other out and create more tension. Recognize that anger signals frustration of some underlying issue. Avoid igniting feelings of anger with the judgment that you are being mistreated. Watch your non-verbal signals, such as your tone of voice, hand and arm gestures, facial expressions, and body movements. Remain seated, don’t stand or march around the room. Deal with one issue at a time. Don’t let your anger about one thing lead you into showering the other with a cascade of issues. If different topics surface during your conflict, note them to address later. Try to notice subtle signs that anger or irritation is building. If you are harboring these feelings, express them before they build too much and lead to an angry outburst. Keep focused on the problem, not persons. Don’t turn a fairly manageable problem into a catastrophe. Emphasize where you agree.
7. Declare your devotion to each other again and again. True long-range intimacy requires repeated affirmations of commitment to your spouse. Remember: love is in both what you say and in how you act. Buy flowers. Do the dishes and take out the trash without being asked. Give an unsolicited back or foot rub. Committed couples protect the boundaries around their relationship. Share secrets with each other more than with any circle of friends and relatives.
8. Give each other permission to change. Pay attention. If you aren’t learning something new about each other every week or two, you simply aren’t observing closely enough. You are focusing on other things more than one another. Bored couples fail to update how they view each other. They act as though the roles they assigned and assumed early in the relationship will remain forever comfortable. Remain constantly abreast of each other’s dreams, fears, goals, disappointments, hopes, regrets, wishes, and fantasies. People continue to trust those people who know them best and who love and accept them.
9. Have fun together. Human beings usually fall in love with the ones who make them laugh, who make them feel good on the inside. They stay in love with those who make them feel safe enough to come out to play. Keep delight a priority. Put your creative energy into making yourselves joyful and producing a relationship that regularly feels like recess.
10. Make yourself trustworthy. People come to trust the ones who affirm them. They learn to distrust those who act as if a relationship were a continual competition over who is right and who gets their way. Always act as if each of you has thoughts, impressions, and preferences that make sense, even if your opinions or needs differ. Realize your spouse’s perceptions will always contain at least some truth, maybe more than yours, and validate those truths before adding your perspective to the discussion.
11. Forgive and forget. Don’t be too hard on each other. If your passion and love are to survive, you must learn how to forgive. Ephesians 4:32 must always be front and center. You and your spouse regularly need to wipe the slate clean so that anger doesn’t build and resentment fester. Holding on to hurts and hostility will block real intimacy. It will only assure that no matter how hard you otherwise work at it, your relationship will not grow. Do what you can to heal the wounds in a relationship, even if you did not cause them. Be compassionate about the fact that neither of you intended to hurt the other as you set out on this journey.
12. Cherish and applaud. One of the most fundamental ingredients in the intimacy formula is cherishing each other. You need to celebrate each other’s presence. If you don’t give your spouse admiration, applause, appreciation, acknowledgement, the benefit of the doubt, encouragement, and the message that you are happy to be there with them now, where will they receive those gifts? Be generous. Be gracious. One of the most painful mistakes a couple can make is the failure to notice their own mate’s heroics. These small acts of unselfishness include taking out the trash, doing the laundry, mowing the lawn, driving the carpool, preparing the taxes, keeping track of birthdays, calling the repairman, and cleaning the bathroom, as well as hundreds of other routine labors. People are amazingly resilient if they know that they are appreciated. Work hard at noticing and celebrating daily acts of heroism by your mate.