Tyramine is a big trigger for me - its occurs naturally in aged foods like mature cheese, dried meats, mould rind or blue cheese, processed meats , and in a lot of normal food when they start to get a bit "past it" in terms of freshness - pre made orange juice is not all that fresh for example!
Lots of people never work out that its the tyramine that is the cause, because your sensitivity to tryamine can be very variable, so a lump of blue cheese might only trigger a migraine if you are stressed or at a certain point in your cycle, or if you have eaten some other high tyramine foods in the day or two proceeding.
I only worked it was a trigger for me after I started eating paleo - no grain, no cheese, no processed foods, I had a big reduction in migraine frequency and it became a lot more obvious that if I cheated on my diet by eating blue cheese or marmite or other high tyramine foods, I'd get an aura starting anything between 15 mins (the marmite!) to about 18 hrs later.
Prior to going on the paleo diet I had so many migraines it was difficult to actually see any pattern of cause because I had so many of them - often several a week.
It might be worth all you frequent sufferers reading up on tyramine foods and cutting them out for a couple of months - with a bit of experimentation people usually find they are fine with a certain amount (I'm ok with coffee and tomatoes, cured meats as long as I don't overdo it), but there may be some things you need to avoid long term - likely to be blue, mouldy and aged cheeses, an sadly, marmite (I love the stuff, but it doesn't love me 
!)