Have Your Own Individual Interests as Well as Joint Interests

Have your own friends, hobbies, and interests outside of the relationship. This has several benefits. It allows you time away from each other when friction begins between you, as well as brings new energy into the relationship if each of you feel rewarded outside of the relationship.

This also allows you to try out things that might become joint interests and you both could enjoy.

Don't Forget to Date

Remember how it felt when you first started dating? You did nice things for each other to show your love (like flowers, surprises, romantic evenings...), you were very considerate of each others, and you looked at dating as a way to learn more about the person. Keep this tradition going. Let your partner know something you like about them, something they do that makes you proud of them or that you admire. Copied from the web.

Buy your partner a card with a sweet thought and slip it in their lunch, remember to kiss hello and goodbye, cuddle, hold hands, etc... and keep romance going. Make a point to learn new things about your partner and share things about you.

Be Supportive

Be supportive of your partner by finding new ways to help them. This may mean simply asking what you can do to help them, or offering a "gift" of additional unexpected aid. For example,

take the kids out so they can have a night at home in peace and quiet
babysit so they can go out with friends one evening
arrange to come home early so they can study while you take care of other details Copied from the web.
walk the dog for them
give them a compliment when you know they need a little ego-boost

It can also mean something like going to church with them, being extra nice during a visit to their family, doing a chore you know they dislike for them, or simply letting your partner decide some issue that is important to them, simply because you know how much it means to them.

Be Physical

Don't let the physical side of the relationship slip away. That may mean sex sometimes, but it also means holding hands, cuddling on the couch in front of a movie, a hug at the end of a tough day, a back or temple massage....

Clear the Air

Routinely build in a time to talk about any unresolved issues over the week. This is especially important if one of you comes from a family that avoided problems, or if you tend to "stew" before you say something. It is also important after big changes, like working more overtime, significantly changing household responsibilities, or making a change in your relationship (like dating exclusively or moving in together). Talk about the small things so they don't become big things.