Don’t speak badly about your spouse. Off-handed remarks you make to others in attempt to be funny are often hurtful. Try to avoid even thinking badly about your spouse. What’s going on in your head will come out in your attitude, even if you don’t say the words. Remember most human communication is in body language and tone of voice, not actual spoken words.
Don’t let others (friends, siblings, parents) speak badly about your spouse either; don’t let them make you the martyr and your spouse the jerk. Be more courteous to your spouse than to any other human. Those little acts of kindness build substantial trust. The comfortable familiarity that follows is a great asset to your partnership. Protect it and expand upon it.