Use clean containers of heavy, opaque plastic with screw-on caps. The American Red Cross suggests clean plastic soft drink bottles (it's very difficult to clean them), food-grade plastic containers or drums. Don't reuse plastic milk containers, since they are extremely difficult to clean completely and can contaminate your stored water. There are a number of commercial water storage containers available designed for storing drinking water.
You can also buy commercially bottled "spring" or "drinking" water and store it for up to a year.