My migraines are somewhat atypical in that I don't get one sided face pain, and only a little little nausea or light sensitivity. I do get a small visual disturbance, like a curved drop of water on a camera lens, about the size of a grain of rice. It's always on the right of my visual field. It appears and then it starts getting bigger. ( I immediately take 3 aspirin asap when this visual thing starts happening, which really helps, and the sooner I take them the better. )
Soon the disturbance grows until it fills my visual field with flashing lights, gradually heading towards the outer right of my visual field where it then disappears. I can see right through these lights..it's sort of like the effect you get if you blink over and over really fast.
A few minutes after the disturbance disappears I start to get a wicked neck headache and my eye sockets get pretty tender. As I said, I'm lucky in that I don't get more than just a bit nauseas, I just get a little light sensitive ( which I am anyway ), and I don't get the one sided face pain. I also don't have to check out for a few hours, I can function right through them. Within several hours the worst of it is gone, thought my eye sockets remain a bit tender for a day or two.
Every single one I've had is very, very similar to the above description. I began to notice that certain activities involving holding my neck in certain ways would bring them on. I even found a place on my neck that I could press and initiate one. I tested it twice and never did it again!
So...I started working with special attention to lifting my chest and back, and bringing my chin down and head back a little. Really just standard good upper body posture. I also generally avoid locking my knees, always trying to maintain at least a little springy bend in them. Not locking the knees when standing goes a long way towards strengthening the legs. If you look around at other people as well as yourself, you will see that most people lock their knees when standing. I also work at maintaining what I call a "leveling" pelvis and an "uprighting" spine.
I use the "-ing" ending here because some people think the pelvis should be level all the time and the spine upright all the time. I find this makes for a very held, artificial, rigid body that is the opposite of what I want. So I allow for the necessary distortions of perfect pelvic and spinal alignment that moving demands, but within these movements and whenever I stop moving, I want my pelvis to be seeking a level position (as opposed to holding a level position ) and the same with the spine. So I say "leveling" and "uprighting" rather than "level" and "upright".
With the strong springy leg thing going, the leveling pelvis, the uprighting spine, and uprighting head, things have improved quite a bit. Once I discovered taking aspirin immediately that helped too. I also don't identify myself as a "migraine sufferer" and I don't let whatever pain I'm in stop me from living my life. I just do what I'd normally do, with the pain in the background instead of as my main focus. Most people who know me don't even know that I get these headaches.
I used to get a few a month! I was always about to get one, having one, or getting over one, and they took days to dissipate. Now, I get them about once a year and the only time I get them is after riding in a car, particularly if the road is winding. I don't get one every time I'm in a car, but almost every time I get one it's within minutes after getting out of a car. Luckily this is something I really don't do that much. Plane travel used to really kill my neck. Once at my destination, I'd be useless for about 24 hours. But I haven't been in a plane since 1999 and it would be fine with me if I never did for the rest of my life! Sometimes I'll just get a mild version of the headache without the visual disturbance. but again it's almost always connected to neck or eye strain. In general, since working on these posture points, when I do get one, the pain has lessened and goes away faster. I also think that my focus in recent years on drinking plenty of water has helped too, but I have less clear evidence that this is the case.
I know everyone's headaches are different, but good posture couldn't possibly hurt anyone. I strongly recommend Yoga, especially slow careful posture oriented Yoga, and/or T'ai-Chi to build strong postural habits. If you suffer from migraines, attention to your posture might very well help with your symptoms. And whether or not it does help, you have my sympathies.