What are the major causes of food poisoning?
Welcome to the forum! Food poisoning may be due to many reasons, some of which are restaurants leaving food unrefrigerated, not washing produce thoroughly or not cooking meats and eggs to a high enough temperature ( varies among meats, poultry and eggs). Sometimes you can tell it's moldy from smell or color, but  other times, unfortunately, like in the case of E. coli, you can't tell whether  the food is contaminated by the way it looks, smells, or tastes. Try to make sure all food is fully cooked, do not eat dishes with uncooked meats, all raw vegetables should be washed, and do not eat dishes with uncooked eggs. Good luck!