Make time for each other. Have a date night, even if you are broke and watching a movie on the TV at home. The point is spending time together, not spending money.
Never, ever go to bed mad. Settle it. This is usually followed by makeup sex.
Never tell your spouse to sleep on the couch. If you are so mad that you can't imagine sleeping next to them, grab a blanket and take yourself to the couch. Argue over who gets to declare "No, I'm sleeping on the couch!" (It gets funny at this point and hard to keep a straight face.)
Kiss each other good night every single night, even if you just had a fight. This often initiates makeup sex.
Talk.
Actively look for sexy activities to share, like oil massages.
Shop for naughty lingerie together.
Share your fantasies.
Being a lover in marriage is about trust and intimacy. This requires ongoing efforts at communication. It also requires that you invest time in the relationship. It takes at least 15 hours a week to establish and maintain intimacy. Intimacy is the font of good sex when novelty is no longer your shtick.
Remember that all is fair in love and war and this is love, not war. Make up caring exceptions to the rules you were raised with and to hell with what other people think.
Always fight fair. This is your lover. It undermines the relationship to be nasty to them when you disagree and the price you pay for that often shows up in the bedroom.