My triggers are stress, caffeine withdrawal and too much sun, especially sunlight first thing in the morning. If I go out before my eyes are awake, if that makes sense, guaranteed migraine. I try to make it so that I'm awake for a good hour or so before I go out in the morning, even it's to get something from the car. Doesn't always happen of course, but a pre-emptive strike of advil and coffee usually heads it off.
I nearly forgot about my food trigger, I've avoided them for so long, I don't even think about it anymore. I can't drink sodas similar to coke or pepsi. If I do, I'll start getting one in minutes.