It is often claimed outside this sub that arguments are normal in relationships. In fact, some go as far as to say that arguing is good because the strong emotions exhibited are the kind that show you truly care about the relationship. However arguing creates an antagonistic environment. It fosters a "me vs you" atmosphere, rather than a more ideal "me and you vs the world". The strong emotions of that you create in the relationship don't have to be used against the person you love, instead they can be used for him.
In order to stop arguments, it is important to understand why they occur. A typical argument has two components a spark and an ignition.
Spark: The spark is the seed that starts the argument. It can be almost anything, provided that the listener has a negative emotional reaction to it (we'll get to that later). It can be something seemingly innocuous, like mentioning that the pizza is cold, to something disrespectful like saying that someone "can't get anything right". Normally we do not act like, or hang around, someone who would do the latter.... that is why often people will look back on an argument and wonder why they were arguing about something so stupid. That is the spark.
Ignition: The ignition is what happens when someone has a negative emotional reaction to a spark, and responds accordingly. This can manifest itself in either offensive ("You screwed up last time") or defensive ("It's not my fault") behavior. Once the spark is ignited, the argument escalates until one person chooses to end it (either be giving up their position or walking away).
We often hear the common wisdom that an argument takes two people. While this is true, it is important to understand that you can only control one of those people's behavior, your own. Here are some things you can do that can stop arguments before they begin.
Step 1: Don't create the spark. Watch yourself and try to make sure you are not creating sparks in your relationship. If you are nagging, condescending, or rude this is especially important.
In addition to that, try to learn and pay attention to your SO's triggers (we all have them). Does he dislike when you cross your arms? Does he hate when people chew with their mouth open? Does he not like you saying negative things about his mother? Avoid triggers whenever possible, and if you have to go near them, tread cautiously.
However you will not always know what will upset someone (remember sparks can be innocuous) so you can sometimes create a spark by mistake.
Step 2: Don't ignite the spark. If your SO set created the spark do not respond negatively to it. Normally (unless you have chosen a poor captain) your SO will not intentionally make you angry. He may have to tell you that you made a mistake, or he may step on one of your triggers by accident. If this happens you have a choice to not be angry. If you choose not to respond negatively there won't have to be an argument. Ask yourself "is this the hill I want to die on"?
Step 3: Defuse the situation. If step 1 and 2 don't work then there are some techniques to keep the situation from escalating. One typical example is if you create a spark by mistake, he takes it, and now you are standing right at the brink of an argument. Even at this point, you can still choose not to make it an argument, however if can be harder if you let yourself get emotional and angry.
Listen earnestly to what he is saying. An argument is what happens when being right becomes more important than listening. Put away your pride and acknowledge and respond to what he is saying. Whether you believe he is right or not, it it is important to understand where he is coming from so that you can come up with a solution together. Give him his turn to speak, then he will let you have yours. Understand that he thinks he is right just as much as you think you're right (otherwise there wouldn't need to be an argument).
When you prepare to talk to him try to not focus on why there is a disagreement brewing, but rather on how you feel about the situation. If you are able to get angry over this, ask yourself, "why is this so important to me?" Once you do speak, choose your words with deliberation and consideration.
Use noncomplementarity. It is only natural when someone gets angry to want to be angry back and up the ante, that is referred to as "complimentarity". This phenomenon is what keeps arguments going, and what escalates them. One well-known de-escalation technique is to become calmer and quieter if the other person is becoming angrier and louder. Another is to do use counterintutive behaviour, the opposite of what would normally be expected. Try making a joke (not as his expense) or doing something downright silly. If you're lucky you may even get a laugh out of him, either way, if you do it right, it will remind him that you are not the enemy here. When done right this can instantly stop on argument in its tracks.
STFU. As a last resort, if you are angry and want to say something that you know you will regret, keep you mouth shut until you have regained your composure. Not saying anything is better than giving into the argument.
Be willing to be wrong. Remember an argument is most of the time a difference in point of view. Just as you find your reasoning valid, he also finds his reasoning valid. Try to view things from his perspective so that you can at least understand where he is coming from. If you can understand his point of view you can turn any argument into a discussion.
With the right techniques you will start to look like the solution to his life problems, and not like the cause of them. Not all these techniques will work for everyone, in every situation. Choose the ones that work best for your relationship, and the ones that will work for you and your SO.
Lastly, remember one of the benefits of the captain first mate dynamic is it gives an absolute power dynamic. There is no point in arguing because he has the ultimate decision, and he will not listen openly when he is angry. Appealing to reason and his affection towards you are much more effective ways to get him to listen.