1) Simply be more careful with what you eat and drink. Migraine triggers can vary from person to person, but if you find yourself getting a headache, write down the foods or drinks you had shortly before it happened. If you recognize a pattern emerging over time, cut that item or items out of your diet.
2) Make sure you eat regularly. Skipping a meal can sometimes cause migraines.
3) Avoid caffeine, which is also known to be cause for migraines.
4) Even exercise can casue headaches, so taking an anti-inflammatory drug before working out might be a good idea.
5) Changes in sleep patterns can cause migraines, so keep a regular sleep schedule.
6) Stress is one of the biggest migraine triggers, so try to incorporate relaxation methods into your day--whether through meditation, having some quiet time to yourself after work, or maybe even taking an antidepressant if recommended by a doctor.
I disagree about stress as a Migraine trigger. Even the International Headache Society has removed stress from their list of triggers and put it on a list of exacerbating factors that make us more susceptible to our triggers. I have yet to meet a person who didn't find that it is NOT stress that's their trigger, but what they DO or do not do during stessful times that are the triggers. During times of stress, people skip meals, don't drink enough and get dehydrated, don't sleep well, cry, etc. THESE are the triggers.