To prevent dehydration from diarrhea, the document recommends giving specific volumes of oral rehydration solution (ORS) after each stool based on a person's age: 50 ml for infants under 6 months, 50-100 ml for children 6 months to 2 years, and 100-200 ml for those over 2 years. It also advises increasing fluid intake. For treatment, it recommends ORS for home use with no or some dehydration, initial hospital treatment with ORS for dehydration, and IV fluids followed by ORS for severe dehydration. The document lists signs to assess dehydration severity, including increased thirst, dry mouth, and lethargy or unconsciousness indicating severe dehydration.