I'm a pretty laid back person and, if I'm not already stressed to begin with, I tend to have a very long fuse. Mostly because I try not to take anything personally and I give most people the benefit of a doubt. I know from my own experience that I get irritated with people who assume things about my motivations without investigating or getting their facts straight (I loathe the 'you did this to hurt/annoy me on purpose' argument), so I try not to do the same to other people.
It really takes a lot to get me angry--but when I do, I really do. There are only a handful of people in my life who have ever heard me raise my voice or swear or get upset in general and I've been told it's pretty frightening to see me mad. I don't fly off the handle so much as I vouch to tell the truth in the harshest way possible.
The things that set me off are usually unfair behavior, cruelty, and passive-aggressiveness/manipulative behaviour. I can usually stand passive-aggressiveness and manipulative behaviour up to a point; if its directed towards me and I see it, I ignore it. But if its directed towards someone else and its clearly upsetting them and the person doing it has malicious intentions, I get pretty pissed.
And as stated, assumptions about my person or my family and friends tend to be a trigger for me. I'm usually able to recognize it for what it is--a projection of the other individual's unfounded fears, envies, or discomfort rather than anything that I have actually done wrong-- and laugh about it, but if the person is especially needling in their insinuations, I have to remove myself from their vicinity. There is no reasoning with people who have made up their minds about something that doesn't exist and I know that if I engage them aggressively, I'm only giving them the reaction they were looking for. This usually leads to circular argumentation and people bringing up petty, useless crap just so they can say their piece. That kind of selfishness does not mesh with my system at all, especially if I see it being detrimental to the group or project as a whole.
I think the cornerstone for me managing my anger has to do with the fact that I don't like to get angry. I have issues with emotional control--for myself, not others-- and I despise the feeling of letting something so irrational steer my words or actions. Even worse, I dislike the prospect of letting anyone get under my skin so much that they throw off my equilibrium.