1. Make deciding a game instead of a chore.
Try playing "5-3-1" when you're deciding where to eat or what movie to watch, and you're both ambivalent. Person A names five things, Person B eliminates two of the choices, and A eliminates two more — leaving you with one! Whew.
2. Make chores a favor for each other instead of a... chore.
Take turns naming the things that you hate doing the most, and each claim all of the stuff that your partner really despises. Both of your lives will be free of those little annoyances forever, and you'll never have to argue over who's doing more of one thing or another.
3. Talk about the good stuff first.
Institute a rule that when you get off work, the first thing you talk about is the best thing that happened to each of you that day. It could be something as simple as the cute dog on the train or an excellent lunch, but always start your evening with something positive.
4. Take each other out.
Try keeping your "entertainment/dating" budget separate but equal, even after you start combining other finances. Then, alternate weekends of treating each other to everything from ice cream to the movies — no bill-splitting allowed!
5. Use gift-giving occasions as an opportunity to encourage your partner to try something new.
Pushing each other in awesome new directions can be one of the most satisfying things about being in a relationship. Use holidays and birthdays to the effect by buying your partner things like classes, tools, instruments, and other things that will help them broaden their horizons and let them know you believe in them.
6. Prove yourself wrong sometimes.
Take it upon yourself to freely admit that you were wrong on a fairly regular basis. You'll find that it's actually freeing, and your partner will appreciate it and start taking after your example.
7. Don't gloat when you're right.
"To keep your marriage brimming,
With love in the loving cup,
Whenever you're wrong, admit it;
Whenever you're right, shut up."
8. If you agree to let something go and move on, LET IT GO AND MOVE ON.
If there's a thing you can't stop arguing about and it's not going anywhere, it may be time to let it go. Agree to stop talking about it and then actually stop talking about it. Like never, ever bring it up again.
9. Three word-related rules: Say "thank you" a lot more, say "sorry" a lot less, and stop saying "but" entirely.
Don't say "sorry," or talk about how much you suck just because you want your partner to feel bad for you. "Sorry" should be sacred and reserved for when you really mean it, and it cheapens your relationship to use it as a manipulation tactic.
Say thank you all the time: Like, so much that it feels weird. Say it about the silliest, tiniest things and about the big things. Your partner will never get tired of it, promise.
Outlaw the word "but." ESPECIALLY when it follows "I love you." Use "and" instead.
10. Take breaking up off the table when you're fighting.
Mutually agree that if you're going to break up, that decision will be made during a calm discussion, not in the middle of a heated battle. And if one of you breaks the rule and brings up breaking up while you're fighting, stay calm and take a break from the discussion.
11. Find a way to take a break from fighting when you need it.
Come up with a safe word or phrase that indicates that you need a break from the conversation or fight. Sometimes arguments start coiling in on themselves to the point that you're only arguing about the argument — at that point, one of you should be able to say "Pause" and get 15–30 minutes for both of you to cool down and regroup. You may just find that you love each other all over again once the break is over.
12. Reward honesty, even when it sucks.
Make a deal that every time that one of you says something that's difficult to say, that person is rewarded with a kiss. Make admitting fears and doubts about your relationship something that can result in a positive conversation, instead of something to be afraid of.
13. Resist the urge to correct your partner.
While talking openly is important, there are things that can be kept to yourself. One of them is when your partner is wrong about something super trivial. You may not always be able to resist the urge to correct them over who wrote a book or who's singing a song, but try to keep your mouth shut some of the time. Also, if your partner starts telling you a story you've heard before: Just let it go. Maybe there will be a new detail, and either way it's not worth hurting their feelings over a couple minutes of your time.
14. Collaborate on a long list of things you've always wanted to do in your own city.
Designate a night of the week (or month, if you're both busy) where you'll take turns picking something on the list and crossing it off.
15. Go to bed angry sometimes.
Staying up all night fighting, especially on a night when you have to work the next day, isn't helping anyone. You may find when you wake up the next day that you don't even remember what you were so worked up about.