Some quotes from my married friends:

1. Never assume.
2. Compliment more than you criticize.
3. For each time you vent about your husband/wife to your friends, tell three positive stories.
4. Remember that it is ok to do things differently (e.g. there is more than one way to peel a potato or fold the laundry).
5. Always make time for the two of you.
6. Marry someone that you enjoy listening and talking to.
7. Remember that marriage is sometimes a bed of roses and sometimes there are thorns.
8. Remember that the best gift that you can give your children is to love their mother/father.
9. Be fair! Split the housework, spending money, etc evenly. This way you are never resentful of your partners contributions (or lack of) or expenditures.
10. Never go to bed angry. (Unless it's 3a.m. and you're exhausted, angry, and not thinking straight.)
11. Remember that people do fight. It's how you do it that matters.
12. Before starting an argument, consider if it's really worth it.
13. Fight naked.
14. Agree to disagree.
15. Never, ever mention the "D" word (divorce).
16. Do you want to be right or do you want to be married?
17. Respect each other's privacy.
18. Remember that "love is like childhood. You need to learn to share."
19. Marriage is not 50/50, it's two people giving 100/100 all of the time.
20. Surprise each other now and then.
21. The secret to a happy marriage is two TV's!
22. Have date night!
23. Never pass up an opportunity to say "I love you".
24. Hold hands.
25. Hug & kiss every day (several times a day actually!).
26. Always believe that you got better than you deserved.
27. Be quick to say "I'm sorry".
28. Choose the one you love, then love the one you choose.
29. Keep the in-laws out of your marriage!
30. Love isn't always a feeling, it's a decision.
31. Hang in there. It's worth it.
32. Play nice, play often, love much.
33. Never air your dirty laundry as a couple in public.
34. Never keep secrets from each other.
35. Be each other's champion. No matter what, take your husband or wife's side first!
36. Communication is the key!
37. Always respect each other.
38. Never underestimate the power of a good belly-laugh and don't be afraid to laugh at yourself.
39. It's the little things that matter most.
40. Never use the words 'Always' and 'Never' in a fight.
41. It's ok to argue, but never use curse words to express your anger.

Communication.