MEN: Try to not be grouchy or burdensome to your wife when you come home each day. She has had burdens and pressures during her day, especially if you have children. Many wives long to talk about the day when the husband comes home. You may need opportunity to gather your strength, but understand that your wife will need to talk to you as soon as you are calm and able.
When your wife wants to discuss something or says that something matters to her, never discount it. Things matter to women and can be emotionally charged in ways that a man might never understand. Give full weight to what your wife says and deal with it as an issue that is very real to her.
Be attractive to your wife. Call her during the day to show interest and that you think about her, especially during nida when calling is a way of saying that your love is unconditional and constant, when your options for expressing affection are limited. Women like to be made to feel that their husband considers her important. This can be achieved by bringing (or sending) presents, even of the "no cost/low cost" variety. This works with most women (unless they are spoiled, immature, greedy or materialistic) even if you just buy a sentimental card, write a poem or, in some other effective way, demonstrate - on a fairly steady basis - that you are thinking of her, appreciate her and that she matters to you. Whatever you do, it must be sincere and believable. If you will be coming home late, call to say that you are going to be late. Give an estimated time of arrival (call again if this will be significantly changed) and a general explanation of why you are running late (you do not owe her a detailed or minute-by-minute explanation).
Wives object when they are not consulted about bigger decisions. Make her feel part of your decision-making. Give consideration to her opinions about the issue and feelings about being part of the process, even if she will not end up a major contributor to the end decision. In some areas, the woman should be favored in determining a decision because the thing matters very much to a woman or because she understands the subject better than her husband does (even if he does not recognize or admit it). Of course, whenver your wife sees you acting on her input; she will feel loved, happy and appreciated.
Don't give a mere allowance. A wife typically needs access to funds for managing the house and children, shopping, doctors, clothing, etc. It is degrading to have to come to you for each expense. It can lead to fighting if she gets upset or fears she will not have her needs or those of the house and children. She must feel secure about this. If this is a big issue, there might be something more serious involved (e.g. mistrust, bad hashkafa, inadequate livelihood, need to control) which may require professional help to resolve.
Learn Torah steadily. Let your learning show up in improved midos (character traits), halacha observance, behavior and divray Torah at the table (especially shabos and yom tov). Your wife will admire and respect you more.
WOMEN: It improves the spirituality, quality and atmosphere of a marriage immensely when the wife dovens two times a day and attends a good women's shiur (Torah class) at least one time a week, preferably most every day.
When a husband comes home each day, he does not have the energy to hear his wife's complaints about life, the kids, etc. Don't pester him; analyze his day nor interrogate him like the FBI. Don't treat him like a child or slave. Be his wife, not his mashgiach. Instead of nagging or criticizing, be positive; encourage and express appreciation for good things (e.g. his Torah learning, working on his temper or sloppiness). He only need advise you of how he spends his time in general. He need not advise you in detail where he was and what he did every minute. Violating such principles will drive a husband crazy, make him develope habits of escaping you and make him regret coming home. Let him arrive to a warm welcome each day. Make the effort to have an attractive physical appearance that makes him glad he has come home and which keeps his mind off all other women. Speak softly, sweetly, politely and from your heart. Let his time at home go nicely. Let him settle himself and regain his strength; especially after commuting, long hours or a hard day. Be a wife he wants to come home to, be with and be pleasant to - of his own volition.
Focus on supporting his work, Torah learning, praying with a minyan and his "life mission." The gemora says a wife should "stand her man on his feet."
BOTH: A major part of love for a spouse is the ability to sincerely say (especially about something incomprehensible or worthless to you), "If it is important to you, it is important to me, BECAUSE YOU ARE IMPORTANT TO ME."
Be adaptive. Never be unkind. Err on he side of MORE communication, not less. All communication must be soft, polite and two-sided. NOTHING IS WORTH A FIGHT. Each couple must have a qualified, mutually acceptable Rov to bring all questions, problems and differences to. EVERYTHING is addressed and governed by the Torah. Adopt a policy of, "WE DON'T HAVE FIGHTS, WE HAVE SHAALOS!"