I think something that was useful for me was to realize that when people annoy me, they don't do so as a result of looking at a list of all possible options and choosing the one that pisses me off. They are probably, in their own way, doing the best they can. I think in one of the Dalai Lama's books he mentioned that "everyone is trying to be happy and to avoid suffering". So what people do that might annoy you, is a result of their pursuit of happiness and non-suffering, same as you. Their ideas of what consist happiness and non-suffering may be different from you (and may, in your opinion, be 'wrong'), their methods of doing so may also be different (and also, in your opinion, 'be wrong'), but their aim is the same. Keeping in mind that they might not actually BE wrong just because you think so, and also if they are not making the best decisions, they might not be capable of doing anything better.
All the best in your cultivation of metta