Just some information I have collected and would like to keep for future reference ;o) -

• If you get it have the hotel call their doctor for you. You will get a shot in the backside and several tablets to take and you'll be able to safely get about in 24 hours. Any other course of action - or no action at all - is just plain foolish
  
  
• DO NOT DRINK THE WATER FROM THE TAPS! Be especially careful of this when your guard is down – in your hotel shower and when cleaning your teeth. Keep bottled water in your bathroom at all times.
  
  
• Guys (and Gals?) if you use a blade razor to shave do not rinse it under the tap. Rinse it in bottled water also or you might break out in a rash that is not nice in sensitive areas.
  
  
• Don’t drink using straws as they are washed and re-used in some places.
  
  
• Don’t buy bottled drinks that are kept cool in ice/water slurry in cold chests. Purchase only from refrigerated cabinets.
  
  
• Imodium is a common clinical remedy (A$2.00 app; take 2 tablets straight away and 1 next morning).
  
  
• Carry toilet paper with you everywhere in Bali even if you don’t have Bali Belly. The chance of you finding a good, clean, comfortable, useable, flush toilet when you’re out-and-about in Bali is slim. The chances of you finding good, clean, comfortable, useable toilet paper in public places away from your hotel, even in reasonable restaurants, is almost zero!
  
  
• It is a MYTH that you need let the diarrhoea run its course - the bugs are not flushed out in your bowel motions, though they may be present in it. It is more important to slow the diarrhoea to avoid dehydration. Once the diarrhoea has settled & you’ve had no bowel motions for a couple of days, you can treat it with an increase in your fruit & fibre intake.
  
  
• A recently recommended preventative with solid (no pun intended) support is Raspberry juice – with at least 30%, preferably more, real juice in the blend. Mix it strong – 25% cordial: 75% bottled water. Ellagic acid is the ingredient that makes the difference! Some people have a neat swig every morning before breakfast, about 10 mil of 100% strength, 20 mil for 50% etc. Good for kids.

Source: http://www.filosbali.net/BaliBelly&%20healthissues..htm