I also get classic migraines. One came on this weekend when I was cutting back on coffee. Alot of the time its due to dehydration (usually something health related, like dehydrated by alcohol, sunburn, caffeine withdrawal, salty food, etc) and you can actually avert a migraine by chugging a bottle of water or two before the aura turns into pain town. Or at least when it does its much more tolerable.
If you mess that up, and you get the migraine + nausea chances are you've been dehydrated awhile and your blood volume is low so you need water + salt since your body only has a salt receptor you actually won't be thirsty unless you intake some salt. Like a 1/4 teaspoon we're talking tops. About what you would sprinkle on food. Then immediately chug 1-2 bottles of water as you can tolerate.
Try and avoid cheese and dairy as I heard something pretty interesting about the different composition of proteins in dairy like high in methionine that increases blood viscosity (thicker) and so it gives you more ill health effects from dehydration than other people.
http://jn.nutrition.org/content/137/12/2814.full (related, though doesn't really tie in diary, you'd have to research the protein profile of dairy foods but I suspect, bad)
A big part of a migraine trigger is something like high vasoconstriction, blood viscosity, and dehydration combined with higher blood requirements by the brain, like stress, MSG, caffeine withdrawal, visual work, etc. This is when you get the aura. During this time that the aura is happening (due to insufficient blood flow) the blood vessel cells in the brain panic and release Nitric Oxide to force the arteries to open up and then you are in high blood pressure pain town. Cause the last thing your brain wants is a bunch of shitty sludge blood with a whole bunch of toxins that should've been filtered out pounding against it every heartbeat.
Moral of the story TLDR got an aura drank 2 bottles of water with a lick of salt and closed my eyes for 5 minutes and averted what used to be a 6-7 hour ordeal of laying down and throwing up.