What, if any, are the main factots that can bring on a migrane?

There are lots! These vary greatly from person to person. Typical triggers include stress, menstrual periods, lack of sleep (or too much sleep), strong scents, certain foods, etc. Keeping a migraine journal and noting different things that might have caused your migraine can be very effective!
Many. This question has been answered before, but food items, fatigue, lack of sleep, prolonged fasting and environmental factors are some of the causes.