We have two approaches that generally work for us.
More minor problematic things we will talk about in bed, naked 
Big things that are almost guaranteed to get very emotional, we use an instant messenger. It gives us both the opportunity to compose our replies, take deep breaths, and remember that we are on the same side in the big picture.
I’m not good with confrontation, so I’ve learned to stay silent during such talks. I’ll then mull over what she’s said, write down and outline my feelings, then proceed from there. (I also do the outline thing if I’m the one who’s going to start such a talk…) Gives me the chance to be more objective and calm, instead of yelling back or getting overly emotional.
My first ex-wife liked to bring things up in the middle of the night while I was asleep.
I never got swamped with emotion because I was barely functioning but clearly, did not save the relationship.
My second ex-wife and I never argued. Not even when she left.
(sorry but I can only be a bad example)
Sometimes my husband and I have ‘big’ talks in the car. Both people facing forward makes it less ‘in your face’ so gives a bit more breathing room.
I am perfectly capable of discussing my marriage in a calm and level-headed manner. That’s one of the things my wife hates the most about me.
I think e-mail is better. There’s no character limit, and there isn’t the (perceived) pressure to respond immediately, before digesting and contemplating.
How often are your relationship summits? How long do they last? Can you give me an idea of what this sounds like, maybe about 5 minutes worth?
With the partner who most directly instigated the practice, pretty regularly on a once-a-month basis; with the other partners, who also liked the idea, a bit more at random but having them with the beforementioned 1st partner sort of kicks me to think about suggesting one to the others when I see them.
They last sometimes only 15-20 minutes and sometimes considerably longer. A five-minute sound bite might go something like this…
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x: OK, we talked about maybe going to see the theatrical performance, are you still interested?
y: Yeah, if we can still get the discount tickets. I talked to OtherGirlfriend and we can switch the dates and I can see her the day after instead. She said that would be fine.
x: I have been asked if I have Wednesday free next week. Is that OK with you and I can either hang out with you Tuesday or Sunday afternoon instead?
y: Let’s see… yes, that would work,
{{ skip a few more paragraphs about scheduling… poly scheduling is probably an issue that’s polyamory-specific }}
x: So… how do you feel now that I’ve been going to the voter registration drive these last few weeks? You said you could cook for yourself and eat alone those nights, but are you feeling left out or lonely?
y: Well, maybe some. I admire you for doing it but yes it cuts into our time together.
x: And you said before that you already missed the way we used to sit together on the couch when we weren’t going out together.
Y: Yeah, I don’t mean I expect you to be joined at the hip and not go anywhere without me. I’ve been thinking about it and what would feel best to me. How would you feel about picking maybe 2 primary outside activities that mean the most to you, and you can still do other things but not where they take you out in the evenings once a week? Then we’d have at least 2 evenings together at home plus whatever night we go out.
x: Let me think about that. I like the idea though. I do let people talk me into being on a lot of committees and things. Another things we could do is maybe you look at the list of stuff and let me know if there are any that you’d maybe consider joining or being a part of, and then if you came with me we’d be together doing whatever that is?
y: Well, that might work. Here is how I feel when I come home and the place is dark and you’re out. I’m not saying it is wrong for you to be doing stuff or that I should not just get over it when I feel this way, because I don’t resent you doing your projects, but when I first walk in and you’re not here I just feel all abandoned, somehow.
x: That’s not silly, that’s important. I’m glad you told me that. Would it help if you called me on nights when I was out, and we talked some then, so you heard my voice for awhile when you first came home?
Yeah, my husband’s like that too and it drives me nuts.
If you are too emotionally overwhelmed, walk away. Make sure that your partner knows this is not a rejection. We dealt with this early in our relationship; when I am overwhelmed I remove myself from the situation. Going into another room gives me some space and perspective. My husband would take it as a rejection. We talked about this, and I explained my rationale and that it was not a rejection. It is now hoped that my husband will give me a minute and then come to resume our conversation. To be very explicit, I’m not talking about mind games here. All of this is clear ahead of time.
To generalize that, I guess, make sure your partner understands why you do the things you do when you argue, and vice-versa. It’s very common for actions in the heat of the moment to be misinterpreted and taken in the worst way.
Try to stick to a rule of no personal insults or tantrums. If you do something angry/mean-spirited, apologize immediately.
Hold hands, or just touch one another lovingly as you talk. It’s a constant reinforcement that you are committed and together and that whatever it is you’re discussing, it can’t shake that basic foundation of love.
The rule my wife and I use is to try to remember that while the other person may make mistakes or exhibit weakness they always have good intentions. Try to make the conversations less about what is wrong and who is to blame (I hate that you never do this, or you always do that) and more about suggestions of how to make things even better (I would make me happy if you did this, or if you stopped doing that). The goal is to make these discussions less you vs. him, and more you and he together trying to work out how to improve the marriage.
Also try early on to get less caught up in the details of the argument and concentrate more on the underlying feeling behind it. For example “you always leave your underwear on the bathroom floor for me to pick up” might really be “I feel you as though my work is being taken for granted”. Then once this is discovered you can work on detailed ideas as to how to best resolve the issue.
Wonders which girlfriend AHunter3 could possibly have had that conversation with.
giggle I didn’t feel like being quite so personal as to try to recapture any specific conversation, but I wanted to impart the TYPE of things we discuss and the kind of listening and negotiating and whatnot.