I'm afraid that I must respectfully disagree with your short list. There is nothing remotely unique to the Christian faith in your answer.
The number one "secret" to a good marriage is God. That is, both persons must be willing to be used up of themselves and deny themselves. (Perhaps this is what you meant by "be the right person.") And at the center of that is God.
If a person is actively seeking a mate, then they are not seeking God. We are, after all, instructed to seek God first, and His righteousness. If we can do this, then God might provide us a mate. But then again maybe not.
Having been to several marriage conferences, the one thing I've noticed is this, there is no difference between the advice given in a secular workshop and a Protestant one. (The one Orthodox marriage seminar I attended blew me away. It was deep!) Good communication, his needs her needs, blah, blah, blah.
The couple needs, first and foremeost, to be united in every aspect to God the Father. A couple who agrees together regarding doctrine, theology and worship, and who's own walk with the Lord is taken care of, will have a healthy marriage.
After again reading your own answers, under "Be the right person," you have created an idolitrous situation. You make the spouse the center of attention. The only way I can "be the right person" is to be totaly submissive to God. He must be my focus. If the vertical relationship is in order, the horizontal will work itself out. (Aquire a spirit of peace, and a thousands souls around you will be saved.)
So, here are my "6 Secrets to a good marriage."
1. Married or single, arise every morning for a consistant time of communing with God by yourself.
2. End every day with a consistant time of communing with God by yourself.
3. Begin every day with a time of standing side by side with your spouse at your family altar and praying.
4. End every day standing side by side with your spouse at your family altar praying.
5. Seek first His kingdom and His righteousness (Matt. 6:33)
6. Be holy, as God is holy.
Marriage should be seen as a way that God makes us holy and God is glorified.
Peace.
Peter