On the matter of getting the runs...
On arrival at your destination, deliberately drink just a little (very little) of the local water. Your body will be able to handle it and build up resistance against the newly introduced germs. Each day, drink a little more. Other than that, only coffee... (boiled water).
The water quality need not be bad, but just the different bacteria in it cannot be handled by your body all at once.
Same principle as your flu-shot. You get a little of the flu so your body can build up resistance.
This has always worked well for me. I learned the hard way too, on the first few visits to Asia. On applying this, never had any problem again.
Toon