Well I haven't been married as long as some of these peeps. I was married once before my sweet dh for 2 years-together 5yrs before marriage.
My dh and I were together for 2 years before marriage-now we've been married 5yrs. I knew he was the one because we could talk about anything, he was caring and kind, a huge variety of reasons really.
My advise is to talk about everything before you get married. Kids, religion, careers, where you want to live, what you think is important in life, ect. I know so many people who wait until after they are married only to find out one parent is adamantly against spanking and the other thinks it's the only way to go. Or one thinks spending time with family is more important than money, and the other thinks you don't care about your family unless they don't want for anything material.
I know for my marriage communication has been the key to our happiness.