Pollution can be prevented by decreasing dependency on fossil fuels as source of energy. That is using alternative sources of energy such as wind, hydro electricity, solar, tidal, bio fuels(produced from sugarcane), bio gas. Replace chlorofluorocarbons by fluorocarbons (which do not damage the ozone layer). Decrease the use of fertilizers & fertilizers. Do not dump your wastes near rivers,canals or sea. Factories should use less toxic chemicals, treat their effluents to remove harmful chemicals before disposal, not dump poisonous waste into open drains.
Well that's some of the ways to prevent pollution.