Drink water from commercially sealed bottles or as an alternative go for carbonated beverages. Don’t go for ice as it may be unhygienic. Even for brushing your teeth, use bottled water.
If the country you are going to has a risk of malaria, then do consult your doctor before going. He will prescribe you preventive medicine for malaria which you can take before going on your trip, while traveling and also for four weeks after returning home.
Swimming and other water activities should be avoided in streams and freshwater lakes.
If you are going to a country with an increased risk of mosquito borne diseases, try and protect yourself against insects. Insect repellents containing DEET are the best. Use bed nets and wear permethrin-coated clothing while you sleep.
Avoid using overcrowded transportation. Ride in vehicles having a safety belt and also wear a helmet while driving a motorcycle. Driving at nights and in unfamiliar areas without local help and directions should be avoided.