The first thing I do is try to stop and identify what I'm angry about or frustrated with.
Then I check to see if it's something I can control, and if it's not then I just accept it. I might not like it, but I accept that it's the way things are.
For example I (used to) get angry driving. What I was angry with were bad drivers.
Is it reasonable to expect to drive and not run into bad drivers? No, they're out there and there's nothing you can do a bout it.
What I can do about it is change my reaction. Instead of raging at bad drivers I simply shake my head and continue about my day.
Think of it like you're holding a hulu-hoop. Inside that hulu-hoop are things you can change. Outside the hula-hoop are things you can't change. Getting mad at things you can't change isn't helpful, so concentrate on the things you can control, including your reaction.