I have to admit, I skimmed a bit of this thread, but everything I saw I agree with.
I'm a sufferer and I've had very few people in my life who are supportive and encouraging. Even then, no one in my life understands. A big reason for this is that it's only been in the last few months that I've really been open to the people in my life about it.
Here is my "Code" as I call it for dealing with other people and the reasons I developed these rules for myself. I try to stick to it as closely as possible whether or not the person(s) I'm dealing with know I have PTSD or not. The rules themselves are in bold so if you want to skim to any that apply to you/your person, you can do that. :D
1-If I'm losing my temper, I remove myself from a situation.
I'm not a violent person. My temper is internalized and right now I'm trying to find ways to get it out in a healthy manner. Learning to blow off steam, if you will. I work very hard to not just blow up or yell at people. Alternately, if I walk away from a tense situation and the person doesn't respect my need for space and peace and quiet (a problem growing up with my dad when we had conflicts; he wasn't the abuser) and they follow me or force confrontation and things get ugly, I make it very clear later on after the altercation has passed that when I walk away I am not to be followed or harassed under any circumstances as it is counterproductive and I simply shut down.
2-I try to get a good balance of interaction vs. time alone.
Being alone bothered me as a child and after I left therapy when I was 15 I realized I had codependency issues with some of my friends. I have an outgoing personality no matter how damaged I am, so even though I do have social anxieties I just try to make sure that the social setting I'm involved with is with people I'm comfortable with. Also, having ample time to myself provides me with the ability to think over any of my current problems in peace, have a little escapism (which I think is healthy as long as it doesn't consume your life or get in the way of real human interaction), meditate, read, have hobbies, whatever. It's personal time that helps me center myself.
3-I NEVER let PTSD be an excuse to abuse other people.
Yes, we like everyone else have bad days. For me, those bad days can range anywhere from thoughts of self-harm (which I've learned to channel into hobbies, which for me are creative/productive escapism) to just being mildly depressed. This is a wide range. To follow this rule, I have to be clear about my needs with the people I live with or am around on a daily basis.
Those of us who suffer MUST learn to be clear about our needs, otherwise our interactions will suffer and that will cost us quality of life. For the supporter, if the sufferer isn't clear on those needs or hasn't learned to be clear, patience is a huge thing. Gentle encouragement toward communication is the best way to go about finding out what those needs are.
Some of these needs include how to deal with me when I'm feeling X emotion, how to read my tells when I'm hiding an emotion or trying to fake like I'm alright when I'm really about to have a meltdown, when to leave me alone and when to stay or follow. Also, sometimes we have to be reminded that you can't read our minds or faces. Our emotions seem really obvious to us because we're having them, but for me, my emotional responses are often flip-flopped. I react to anger with crying and sadness with rage, so, for example, I make it clear to leave me alone if I'm crying and if I appear angry it's okay to stay and try to calm me down if you feel like it.
I also make it clear that when I'm feeling an intense or extreme negative emotion, it's almost never okay to touch me, unless you're a man and able to hug me in a way that is both comforting and able to restrain me, should your personal safety be an issue. I have a hard time accepting affection from women when I'm upset because it was my mother who hurt me. (These are my personal needs, which I'm using as an example. Hopefully it helps you ask questions or get answers to specific needs.)
4-I try to always process my feelings instead of ignoring them.
This is one I'm still learning. I'm getting better, but old habits die hard! Being a supporter, it's important to figure out what kind of encouragement your person needs to process. For me, I just have to wallow for a little while. I try to be alone when I do this because I know it's ridiculous. I'm not the pity party type, but so far letting myself be miserable for a little while is the only way to really get it out. For now it will do. But after a few days and sometimes a couple of weeks, I just wake up and tell myself I'm done and it's over. As the supporter, you might just have to make yourself scarce.
Alternately, they may just need someone to cry on. Or yell to. I used the word "to" because yelling to someone is different than yelling "at" them. When I need to scream, I call my best friend, I tell her I need to yell and she just listens while I do it. The same for when I cry. She listens, and when I'm done she responds. Asks me questions, sound boards, helps me problem solve. She's pretty awesome.
But! When I feel like I've snapped at her or snarked at her or taken something out on her, I apologize immediately upon realizing it. That goes back to rule number 3. It's never okay to take things out on other people.
5-I never make my problems someone else's problem.
This is one I only struggle with in a troubles-with-living kind of way. Emotionally, I take responsibility for my baggage as best I can, but I didn't have a childhood so I'm a maladjusted adult. I'm working on this one.
For those who struggle with this in an emotional kind of way, it may be harder on you and harder for them to get this one down. It requires removal of the chip from your shoulder and that separation of shoulder and chip can be a very long and strenuous process. It's about accepting what has happened to you, knowing that it can't be undone, and realizing that you don't have to let it define your future (even if it affects it!) Your damage is not YOU.
6-I never drink when I am: upset, alone, or uncomfortable.
This one is new and also personal to me. If your person becomes angry or hateful when drinking, move on because it doesn't apply to them. This is for people who aren't angry/negative drinkers.
Notice that I didn't include anxious. I'm 23. I like to drink, my friends like to party, it's part of my lifestyle for now. As long as I'm around a few people I'm comfortable with, I feel it is okay for me to drink in any setting whether I'm anxious or not. As long as I'm not upset or feeling negative emotions, alcohol can be very calming to my nerves. Gets me loosened up so I can be funny and entertaining instead of awkward and reclusive. I like to make people laugh. I do this best when I feel good.
7-When in a rut, I try to do something every day that I enjoy and makes me happy.
This usually comes at the end of a wallowing phase I mentioned in rule number 4. I also use this to try to control how I'm feeling when I am having a bad day for no reason. Sometimes I just feel like shit without any reason. When this happens, as soon as I have free time I will do something like an exercise I like, grab a beer in my favorite bar with a friend (as long as I'm just dumpy and not legitimately upset), do a hobby, or just whatever I feel like will make me feel better. Forcing myself to be goofy helps.
As a supporter, when you learn when it's okay to interfere in feelings and when to leave them alone, you can encourage them to do something fun that they really like when they're having a dumpy day. Don't be surprised if they don't want to or if it takes a little pushing. Don't force them, just keep it light and encouraging.
I hope these things help!! I used a lot of personal examples, so some of it may not apply, but I do hope it helps.