Don't eat food purchased from street vendors. Don't drink beverages with ice. Don't eat dairy products unless you know they have been pasteurized. Don't share needles with anyone. Don't swim in fresh water, including Lake Malawi.
Salt water is usually safer.
Iodine tablets and water filters to purify water if bottled water is not available. See Do's above for more detailed information about water filters. Sunblock, sunglasses, hat . This document is not a complete medical guide for travelers to this region. Be sure to read the information about all the regions you are planning to visit.