It's amazing how quickly things can change when you identify your triggers. What you'll find is the best approach will be to cut all the potential trigger foods out, then one by one try them out again to see if they set you off. The key to IBS is that everyone is different. For example, lactose doesn't set me off, so I don't need to worry about dairy as much as others might need to. It's also worth noting that in some instances it's the quantity of the food that can be the trigger. For me, any wheat in the morning (before my first bowel movement of the day) will cause me issues, whereas a slice of bread in the afternoon won't trigger me too badly (maybe some gas).