Prepare Yourself: Many fights occur around predictable issues, either because those issues are a source of repeated, perpetual conflict and / or because they touch on deeply held beliefs or trigger long-held, patterned responses. Examples: If your partner is generally messy and you are a neat freak, or if your partner is a procrastinator and you tend to be Johnny-on-the-spot. It is essentially impossible for one partner to change another's fundamental nature, so it will be counterproductive to criticize that nature. Instead, focus on a specific manifestation of that nature ("It's really important to me that the house be clean when guests come over, so next time please put your tools away;" "Your running late today caused a real problem for me because....").
Examine Your Phrasing: As suggested above, attacks on your partner's basic characteristics are sure to be counterproductive. In fact, ANY attack will most probably be (attack leads to defense, and then each party is locked into a combative position). Practice phrasing your problem with the other's action as complaint (specific to one situation) rather than criticism (a more generalized indictment). A key to improving your performance in this area is to avoid the words "never" and "always" - they not only overly emphasize the severity of the problem, but they are usually untrue (how often does someone "never" or "always" act in a certain way?). Another phrasing tip: whenever possible, begin a sentence dealing with a complaint with "I" rather than with "You". Examples: "You never listen to what I have to say" versus "Sometimes I feel unheard" or "I would like it if I felt you were listening to me more".
Reframe: Remember that your partner is virtually always acting out of his/her own perceived best interests. This is not to suggest that your partner is selfish; it is simply a basic human trait. Too often one half of a partnership will interpret a comment or action as an intentional slight or attack, rather than the more likely explanation - your partner was thinking primarily of his/her needs. Examine some of your past conflicts through this lens and you'll often see another way of interpreting the conflict. Then, practice keeping this principle in mind and bring it into issues as they arise.
Take a timeout: When you find yourself in the middle of a heated discussion, "take your temperature". If you're feeling angry or wounded it will be almost impossible for the discussion to accomplish anything other than further raising the temperature. Reach an agreement with your partner on a signal or phrase that will allow you to disengage, giving you time to quiet down (you'll need at least 15 to 20 minutes if you're like most people) and be able to listen rather than simply react. Prior agreement is necessary so that your partner doesn't feel that you're simply bailing. Also, be sure that both of you acknowledge that you will employ this technique so that you can better understand each other, and not to simply avoid conflict.
Get better at compromising: Although many marital issues can't be addressed through compromise (she wants to have a baby, he doesn't....at least yet, a good number of them can be. Even if you think you are absolutely right and your partner totally wrong, you need to be open to being influenced by your partner's preferences. If you can turn your focus away from getting what you want and towards finding a "win / win" solution, you will soften the conflict and move towards closeness.
What Can I Learn?: One of the, if not the, primary ways we grow as people is through relationships. Anyone who comes into our lives is a potential teacher if we choose to view the person that way. We do have a choice about how we want to hold people: as tormentor, annoyer, supporter, etc. Choosing to view them as teachers is often very difficult, but virtually any conflict can be examined for the lesson that it holds. A valuable way to put yourself into a "what can I learn?" frame of mind is to ask yourself whether you have ever done or said anything along the lines of what is so troubling to you about the other person. You'll almost always discover that the answer is "yes".