And remember keep your own hands clean before you eat.
Some of the easiest places to get ill are where there are large numbers of tourists and the locals have adapted by offering western type food and/or a lot of food is saved, stored and re-heated. You might never have a problem in India, eating Indian food, but suffer in Nepal eating western style food.
It is about the simple things you may deal with on a day to day basis (especially if you are heading to poorer or developing countries).
See diarrhoea and dehydration below as it is normally a symptom of food poisoning, for more advice.
It's something of a lottery with food preparation, storage and hygiene (including yours) the key factors.
Chances are you will probably get some form of diarrhoea at some time during a long trip.
Eating a carnivorous diet you do however run a much higher chance of getting ill (chicken is often reheated).
Just remember, you may go a year and not have a problem or get ill on your first day in somewhere like Crete or Las Vegas.