We never had them written down, but my dad wrote my wife and I a letter on our wedding day, in which he listed all the assumed (but unwritten) "Murphey Family Rules" that he believed would give a base for a happy marriage.
1. Be nice to each other.
2. Always stick together.
3. There's always enough to share.
4. Kiss the cook.
5. Family business is FAMILY business.
6. Husband/wife are each other's #1.
7. Don't try to live beyond your means.
8. Debt bad; savings good
9. Don't do anything stupid.
9a. Don't hang around anyone doing anythign stupid.
I hope to keep them going and raise my kids to believe in them, too.