From my experience, you can not avoid getting ill. Sooner or later (probably sooner) it is going to hit you.
Therefore my advice is, to jump right into it. Eat what the locals eat. Do what the locals do. By this you have at least a bit fun until you have to spend your time sitting and sh*ing.
The human body is great in adapting to those situation. On my first visit to an development country I took more pictures from the window of my toilet than anything else. But since my body got somehow got used to the new environment, I have not been ill on my last few trips.
Final advice for third world travel: Have toilet paper ready. Always!
This is not a good strategy. Besides the other good comments, consider the following:
If you're traveling from place to place, you'll be exposed to a parade of regional bugs that locals, who have more stable habits, will not be. And your schedule (reservations, plans, etc.) may not be able to afford the downtime. Finally, you don't know the health care setup, so you won't always be able to sense if something is substandard.
I spent a day in a hospital in India with a very high fever (delirious) and dehydration due to a bit of uncooked chutney that none of the locals (whom I knew) had problems with. They had to give me an IV to rehydrate me. My main goal was to try to keep it together enough to ensure that the clinic was using a sterile needle for the IV.
Thought this would be obvious: I was not talking about stuff that makes everybody ill. The body does not adapt well to many other things, but still you can get used to many things that make people ill on first contact.
Why do so many travellers get sick first time they enter a country with different hygienic standard, where the local population has no problem?
btw: I lived 2 years in central Africa, just returned from a 'local meal' in Luanda/Angola.
The point is that you don't want to try to be like the locals. The locals in developing countries are not healthy and do suffer from poor sanitation (diarrhea alone is responsible for 8% of all deaths in Asia -- WHO stats). You need to be sensible and avoid certain things.
I just got back from a month in China and didn't get sick despite eating many things that'd make a typical westerner puke. I lived in China for several years previously and had learned the hard way about food safety.
Therefore my advice is, to jump right into it. Eat what the locals eat. Do what the locals do. By this you have at least a bit fun until you have to spend your time sitting and sh*ing.
The human body is great in adapting to those situation. On my first visit to an development country I took more pictures from the window of my toilet than anything else. But since my body got somehow got used to the new environment, I have not been ill on my last few trips.
Final advice for third world travel: Have toilet paper ready. Always!