This is an extremely important point. My wife and I agreed even before the wedding that divorce wasn't an option. We even refrained from mentioning the word. She was a wonderful woman. (She passed away in September after 16 happy years and two years of illness)
Now I find myself soon to be looking for a new wife. I'm kind of leaning toward a pre-nup that states that divorce is not allowed except in the case of adultery, abuse, abandonment or mutual agreement. Since I do not believe in divorce we'll never mutually agree and I won't do the other three so we should be in good shape.
The other important part of marriage, perhaps the most important, is make God the focus of it. As we each draw closer to God we cannot but help drawing closer to each other.
Since my husband and I became Christians, we certainly believe this is the paramount focus of our marriage.