Definitely trust and honesty. I feel like a lot of couples don’t talk about important issues enough, or aren’t 100% honest with their views on certain things. I think right of the bat it is important to talk about the big issues, such as children, parenting ideals, religious/spiritual views, politics, etc. Not every successful couple needs to have the same views, but they need to be accepting of each others individualism. I, personally, think it helps to f(for the most part) see eye to on the major issues. For example, do you and your significant other disagree on how a child should be raised? Do you both want to continue to grow professionally? Is one of you the main bread winner? Are finances separate? Just some thoughts. These are issues that I feel most couples kind of brush under the rug in the beginning of a relationship, and then are afraid to talk about them later because of the fear that they will disagree or it will somehow ruin the “honeymoon” phase. 🙂
Oh yeah, and cuddling. Lots of that.