A good idea is to keep a food journal. For example, some people can eat a meal of chili without any side effects, whereas just one spoonful of chili may send another person into extreme gastrointestinal distress. By keeping a journal, you will soon know which foods disagree with you, and you can learn to stay away from them. Something as obvious as making steady notes of your daily meal intake and noting any symptoms that arise can be enough to cure such things as indigestion, headaches or heartburn.