Safi Khan, in his “Marriage 101″ lecture CD (available from here), mentions many points; of the best, he mentions the following:

  1. For Brothers: use extreme compassion and mercy towards your wives! Almost all relationships could benefit from more mercy and compassion.
  2. For Sisters: struggle not to complain! Once complaints start, they only get worse, and in the end, they can spoil your marriage.
  3. For Both:
  4. have a common goal–to serve Allah (سبحانه وتعالى), to worship Him, and to enter Jannah together, without reckoning.
  5. close the doors of fitnah – shut them off from your marriage. Keep each other’s secrets, don’t share them. Throw out your TV. Travel together on long trips.
  6. worship Allah (سبحانه وتعالى) together – choose some activity that you use, that you do together. Go to Islamic lectures. Read tafseer together. Start an Islamic project. Memorize Qur’an together.