For me the number one trigger was caffeine, but because I'd never had that much, doctors just said it was probably stress, so I didn't eliminate it. Also because this all happened when I was a kid, I didn't have the wherewithal / knowledge to try an elimination diet. I was an anxious kid so my parents just accepted this "diagnosis" of stress as the main trigger (it definitely is one factor). I cut out caffeine to help me sleep better (after about 14 years of migraines of varying frequency and severity), and found my baseline (monthly, moderate severity) migraines almost completely vanished. Now I only get them if my sleep or food schedule or amounts are seriously disturbed.