This topic will take way more than one post, but let's start with 3 tips. These 3 tips are a mind-set, practical tips will come later.
1. Your marriage is the center of the family.
Yes, that's right, I'll say it again. Your marriage is the center of the family. The children are like little planets that orbit around the parents. Now, this doesn't mean the children are neglected or get no attention. This also doesn't mean it takes 24 hours to cater to your marriage. Here's one example, you and your husband are talking, your kid keeps interrupting and demanding your attention. You say, "mommy and daddy are talking, when we are done, then we can listen to you."
2. Make time for each other.
Everyday, be together for a given amount of time. Tell the kids "this is mommy & daddy time". It could be in bed together in the morning, in the morning over coffee, in the evening after the kids go to bed. Every week, go out on a date. If you can, every month or year go away overnight. This takes planning, especially if you have little, little ones at home, a nursing baby or limited child-care.
3. You and your husband are a team.
When kid issues come up. Discuss them together. Get on the same page and then present your decision to the child.